Solve the integral $int_0^1int^1_xy^4e^{xy^2}dydx$.












1












$begingroup$



Solve the integral $int_0^1int^1_xy^4e^{xy^2}dydx$.




I think that variables substituation is neede here. I've substitute
$$
\ left{begin{matrix}
u=xy^2\
v=y
end{matrix}right.
$$

and calculated
$$\J=begin{vmatrix}
y^2 & 2xy\
0 & 1
end{vmatrix}=y^2
$$

Then, the new integrand is $v^2e^u$. But what is the new domain? Thanks.










share|cite|improve this question









$endgroup$








  • 1




    $begingroup$
    Maybe try reversing order of integration?
    $endgroup$
    – Zachary Selk
    Jan 6 at 17:44






  • 2




    $begingroup$
    Obviously, $$x=u/v^2qquad v=y$$ hence the domain $$0<x<y<1$$ translates as $$0<u/v^2<v<1$$ that is, $$0<u<v^3<1$$
    $endgroup$
    – Did
    Jan 6 at 17:46












  • $begingroup$
    @ZacharySelk Ok, but then, what meaning does the $x$ in the lower bound of the external integral have: $int_x^1int_0^1 A dxdy$ (if $A$ is the integrand)?
    $endgroup$
    – J. Doe
    Jan 6 at 17:52






  • 1




    $begingroup$
    Draw a picture of the region.
    $endgroup$
    – Zachary Selk
    Jan 6 at 17:53






  • 1




    $begingroup$
    Yeah now it's totally doable.
    $endgroup$
    – Zachary Selk
    Jan 6 at 18:12
















1












$begingroup$



Solve the integral $int_0^1int^1_xy^4e^{xy^2}dydx$.




I think that variables substituation is neede here. I've substitute
$$
\ left{begin{matrix}
u=xy^2\
v=y
end{matrix}right.
$$

and calculated
$$\J=begin{vmatrix}
y^2 & 2xy\
0 & 1
end{vmatrix}=y^2
$$

Then, the new integrand is $v^2e^u$. But what is the new domain? Thanks.










share|cite|improve this question









$endgroup$








  • 1




    $begingroup$
    Maybe try reversing order of integration?
    $endgroup$
    – Zachary Selk
    Jan 6 at 17:44






  • 2




    $begingroup$
    Obviously, $$x=u/v^2qquad v=y$$ hence the domain $$0<x<y<1$$ translates as $$0<u/v^2<v<1$$ that is, $$0<u<v^3<1$$
    $endgroup$
    – Did
    Jan 6 at 17:46












  • $begingroup$
    @ZacharySelk Ok, but then, what meaning does the $x$ in the lower bound of the external integral have: $int_x^1int_0^1 A dxdy$ (if $A$ is the integrand)?
    $endgroup$
    – J. Doe
    Jan 6 at 17:52






  • 1




    $begingroup$
    Draw a picture of the region.
    $endgroup$
    – Zachary Selk
    Jan 6 at 17:53






  • 1




    $begingroup$
    Yeah now it's totally doable.
    $endgroup$
    – Zachary Selk
    Jan 6 at 18:12














1












1








1





$begingroup$



Solve the integral $int_0^1int^1_xy^4e^{xy^2}dydx$.




I think that variables substituation is neede here. I've substitute
$$
\ left{begin{matrix}
u=xy^2\
v=y
end{matrix}right.
$$

and calculated
$$\J=begin{vmatrix}
y^2 & 2xy\
0 & 1
end{vmatrix}=y^2
$$

Then, the new integrand is $v^2e^u$. But what is the new domain? Thanks.










share|cite|improve this question









$endgroup$





Solve the integral $int_0^1int^1_xy^4e^{xy^2}dydx$.




I think that variables substituation is neede here. I've substitute
$$
\ left{begin{matrix}
u=xy^2\
v=y
end{matrix}right.
$$

and calculated
$$\J=begin{vmatrix}
y^2 & 2xy\
0 & 1
end{vmatrix}=y^2
$$

Then, the new integrand is $v^2e^u$. But what is the new domain? Thanks.







integration multivariable-calculus substitution jacobian






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Jan 6 at 17:43









J. DoeJ. Doe

14510




14510








  • 1




    $begingroup$
    Maybe try reversing order of integration?
    $endgroup$
    – Zachary Selk
    Jan 6 at 17:44






  • 2




    $begingroup$
    Obviously, $$x=u/v^2qquad v=y$$ hence the domain $$0<x<y<1$$ translates as $$0<u/v^2<v<1$$ that is, $$0<u<v^3<1$$
    $endgroup$
    – Did
    Jan 6 at 17:46












  • $begingroup$
    @ZacharySelk Ok, but then, what meaning does the $x$ in the lower bound of the external integral have: $int_x^1int_0^1 A dxdy$ (if $A$ is the integrand)?
    $endgroup$
    – J. Doe
    Jan 6 at 17:52






  • 1




    $begingroup$
    Draw a picture of the region.
    $endgroup$
    – Zachary Selk
    Jan 6 at 17:53






  • 1




    $begingroup$
    Yeah now it's totally doable.
    $endgroup$
    – Zachary Selk
    Jan 6 at 18:12














  • 1




    $begingroup$
    Maybe try reversing order of integration?
    $endgroup$
    – Zachary Selk
    Jan 6 at 17:44






  • 2




    $begingroup$
    Obviously, $$x=u/v^2qquad v=y$$ hence the domain $$0<x<y<1$$ translates as $$0<u/v^2<v<1$$ that is, $$0<u<v^3<1$$
    $endgroup$
    – Did
    Jan 6 at 17:46












  • $begingroup$
    @ZacharySelk Ok, but then, what meaning does the $x$ in the lower bound of the external integral have: $int_x^1int_0^1 A dxdy$ (if $A$ is the integrand)?
    $endgroup$
    – J. Doe
    Jan 6 at 17:52






  • 1




    $begingroup$
    Draw a picture of the region.
    $endgroup$
    – Zachary Selk
    Jan 6 at 17:53






  • 1




    $begingroup$
    Yeah now it's totally doable.
    $endgroup$
    – Zachary Selk
    Jan 6 at 18:12








1




1




$begingroup$
Maybe try reversing order of integration?
$endgroup$
– Zachary Selk
Jan 6 at 17:44




$begingroup$
Maybe try reversing order of integration?
$endgroup$
– Zachary Selk
Jan 6 at 17:44




2




2




$begingroup$
Obviously, $$x=u/v^2qquad v=y$$ hence the domain $$0<x<y<1$$ translates as $$0<u/v^2<v<1$$ that is, $$0<u<v^3<1$$
$endgroup$
– Did
Jan 6 at 17:46






$begingroup$
Obviously, $$x=u/v^2qquad v=y$$ hence the domain $$0<x<y<1$$ translates as $$0<u/v^2<v<1$$ that is, $$0<u<v^3<1$$
$endgroup$
– Did
Jan 6 at 17:46














$begingroup$
@ZacharySelk Ok, but then, what meaning does the $x$ in the lower bound of the external integral have: $int_x^1int_0^1 A dxdy$ (if $A$ is the integrand)?
$endgroup$
– J. Doe
Jan 6 at 17:52




$begingroup$
@ZacharySelk Ok, but then, what meaning does the $x$ in the lower bound of the external integral have: $int_x^1int_0^1 A dxdy$ (if $A$ is the integrand)?
$endgroup$
– J. Doe
Jan 6 at 17:52




1




1




$begingroup$
Draw a picture of the region.
$endgroup$
– Zachary Selk
Jan 6 at 17:53




$begingroup$
Draw a picture of the region.
$endgroup$
– Zachary Selk
Jan 6 at 17:53




1




1




$begingroup$
Yeah now it's totally doable.
$endgroup$
– Zachary Selk
Jan 6 at 18:12




$begingroup$
Yeah now it's totally doable.
$endgroup$
– Zachary Selk
Jan 6 at 18:12










2 Answers
2






active

oldest

votes


















5












$begingroup$

$newcommand{bbx}[1]{,bbox[15px,border:1px groove navy]{displaystyle{#1}},}
newcommand{braces}[1]{leftlbrace,{#1},rightrbrace}
newcommand{bracks}[1]{leftlbrack,{#1},rightrbrack}
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newcommand{ds}[1]{displaystyle{#1}}
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newcommand{totald}[3]{frac{mathrm{d}^{#1} #2}{mathrm{d} #3^{#1}}}
newcommand{verts}[1]{leftvert,{#1},rightvert}$




$ds{int_{0}^{1}int_{x}^{1}y^{4}expo{xy^{2}}dd y,dd x:
{LARGE ?}}$
.




begin{align}
&bbox[10px,#ffd]{int_{0}^{1}int_{x}^{1}y^{4}expo{xy^{2}}dd y,dd x} =
int_{0}^{1}y^{4}int_{0}^{y}expo{xy^{2}}dd x,dd y =
int_{0}^{1}y^{4}{expo{y^{3}} - 1 over y^{2}},dd y
\[5mm] = &
int_{0}^{1}pars{y^{2}expo{y^{3}} - y^{2}}dd y =
left.{expo{y^{3}} - y^{3} over 3},rightvert_{0}^{1} =
bbx{expo{} - 2 over 3} approx 0.2394
end{align}






share|cite|improve this answer









$endgroup$





















    2












    $begingroup$

    Well, solving a much more general problem:



    $$mathcal{I}_text{n}left(alpharight):=int_0^alphaint_x^alphatext{y}^text{n}cdotexpleft(xcdottext{y}^{text{n}-2}right)spacetext{d}text{y}spacetext{d}xtag1$$



    Using that (for all $x$):



    $$expleft(xright)=sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}tag2$$



    We can write:



    $$mathcal{I}_text{n}left(alpharight)=int_0^alphaint_x^alphatext{y}^text{n}cdotsum_{text{k}=0}^inftyfrac{left(xcdottext{y}^{text{n}-2}right)^text{k}}{text{k}!}spacetext{d}text{y}spacetext{d}x=$$
    $$int_0^alphaint_x^alphatext{y}^text{n}cdotsum_{text{k}=0}^inftyfrac{x^text{k}cdottext{y}^{text{k}left(text{n}-2right)}}{text{k}!}spacetext{d}text{y}spacetext{d}x=$$
    $$int_0^alphaleft{sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}int_x^alphatext{y}^text{n}cdottext{y}^{text{k}left(text{n}-2right)}spacetext{d}text{y}right}spacetext{d}x=$$
    $$int_0^alphaleft{sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}int_x^alphatext{y}^{text{n}+text{k}left(text{n}-2right)}spacetext{d}text{y}right}spacetext{d}x=$$
    $$int_0^alphaleft{sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}cdotleft[frac{text{y}^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}right]_x^alpharight}spacetext{d}x=$$
    $$int_0^alphaleft{sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}cdotleft(frac{alpha^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}-frac{x^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}right)right}spacetext{d}x=$$
    $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotleft{frac{alpha^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}cdotint_0^alpha x^text{k}spacetext{d}x-frac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotint_0^alpha x^{1+text{n}+text{k}left(text{n}-1right)}spacetext{d}xright}=$$
    $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotleft{frac{alpha^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}cdotfrac{alpha^{1+text{k}}}{1+text{k}}-frac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotfrac{alpha^{1+1+text{n}+text{k}left(text{n}-1right)}}{1+1+text{n}+text{k}left(text{n}-1right)}right}=$$
    $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotleft{frac{alpha^{2+text{n}+text{k}left(text{n}-1right)}}{1+text{n}+text{k}left(text{n}-2right)}cdotfrac{1}{1+text{k}}-frac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotfrac{alpha^{2+text{n}+text{k}left(text{n}-1right)}}{2+text{n}+text{k}left(text{n}-1right)}right}=$$
    $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotfrac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotleft{frac{alpha^{2+text{n}+text{k}left(text{n}-1right)}}{1+text{k}}-frac{alpha^{2+text{n}+text{k}left(text{n}-1right)}}{2+text{n}+text{k}left(text{n}-1right)}right}tag3$$



    When $alpha=1$, we get:



    $$mathcal{I}_text{n}left(1right):=int_0^1int_x^1text{y}^text{n}cdotexpleft(xcdottext{y}^{text{n}-2}right)spacetext{d}text{y}spacetext{d}x=$$
    $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotfrac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotleft{frac{1}{1+text{k}}-frac{1}{2+text{n}+text{k}left(text{n}-1right)}right}=$$
    $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotfrac{1}{1+text{k}}cdotfrac{1}{2+text{n}+text{k}left(text{n}-1right)}tag4$$






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      2 Answers
      2






      active

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      2 Answers
      2






      active

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      active

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      active

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      5












      $begingroup$

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      $ds{int_{0}^{1}int_{x}^{1}y^{4}expo{xy^{2}}dd y,dd x:
      {LARGE ?}}$
      .




      begin{align}
      &bbox[10px,#ffd]{int_{0}^{1}int_{x}^{1}y^{4}expo{xy^{2}}dd y,dd x} =
      int_{0}^{1}y^{4}int_{0}^{y}expo{xy^{2}}dd x,dd y =
      int_{0}^{1}y^{4}{expo{y^{3}} - 1 over y^{2}},dd y
      \[5mm] = &
      int_{0}^{1}pars{y^{2}expo{y^{3}} - y^{2}}dd y =
      left.{expo{y^{3}} - y^{3} over 3},rightvert_{0}^{1} =
      bbx{expo{} - 2 over 3} approx 0.2394
      end{align}






      share|cite|improve this answer









      $endgroup$


















        5












        $begingroup$

        $newcommand{bbx}[1]{,bbox[15px,border:1px groove navy]{displaystyle{#1}},}
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        $ds{int_{0}^{1}int_{x}^{1}y^{4}expo{xy^{2}}dd y,dd x:
        {LARGE ?}}$
        .




        begin{align}
        &bbox[10px,#ffd]{int_{0}^{1}int_{x}^{1}y^{4}expo{xy^{2}}dd y,dd x} =
        int_{0}^{1}y^{4}int_{0}^{y}expo{xy^{2}}dd x,dd y =
        int_{0}^{1}y^{4}{expo{y^{3}} - 1 over y^{2}},dd y
        \[5mm] = &
        int_{0}^{1}pars{y^{2}expo{y^{3}} - y^{2}}dd y =
        left.{expo{y^{3}} - y^{3} over 3},rightvert_{0}^{1} =
        bbx{expo{} - 2 over 3} approx 0.2394
        end{align}






        share|cite|improve this answer









        $endgroup$
















          5












          5








          5





          $begingroup$

          $newcommand{bbx}[1]{,bbox[15px,border:1px groove navy]{displaystyle{#1}},}
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          newcommand{verts}[1]{leftvert,{#1},rightvert}$




          $ds{int_{0}^{1}int_{x}^{1}y^{4}expo{xy^{2}}dd y,dd x:
          {LARGE ?}}$
          .




          begin{align}
          &bbox[10px,#ffd]{int_{0}^{1}int_{x}^{1}y^{4}expo{xy^{2}}dd y,dd x} =
          int_{0}^{1}y^{4}int_{0}^{y}expo{xy^{2}}dd x,dd y =
          int_{0}^{1}y^{4}{expo{y^{3}} - 1 over y^{2}},dd y
          \[5mm] = &
          int_{0}^{1}pars{y^{2}expo{y^{3}} - y^{2}}dd y =
          left.{expo{y^{3}} - y^{3} over 3},rightvert_{0}^{1} =
          bbx{expo{} - 2 over 3} approx 0.2394
          end{align}






          share|cite|improve this answer









          $endgroup$



          $newcommand{bbx}[1]{,bbox[15px,border:1px groove navy]{displaystyle{#1}},}
          newcommand{braces}[1]{leftlbrace,{#1},rightrbrace}
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          $ds{int_{0}^{1}int_{x}^{1}y^{4}expo{xy^{2}}dd y,dd x:
          {LARGE ?}}$
          .




          begin{align}
          &bbox[10px,#ffd]{int_{0}^{1}int_{x}^{1}y^{4}expo{xy^{2}}dd y,dd x} =
          int_{0}^{1}y^{4}int_{0}^{y}expo{xy^{2}}dd x,dd y =
          int_{0}^{1}y^{4}{expo{y^{3}} - 1 over y^{2}},dd y
          \[5mm] = &
          int_{0}^{1}pars{y^{2}expo{y^{3}} - y^{2}}dd y =
          left.{expo{y^{3}} - y^{3} over 3},rightvert_{0}^{1} =
          bbx{expo{} - 2 over 3} approx 0.2394
          end{align}







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Jan 6 at 21:48









          Felix MarinFelix Marin

          67.9k7107142




          67.9k7107142























              2












              $begingroup$

              Well, solving a much more general problem:



              $$mathcal{I}_text{n}left(alpharight):=int_0^alphaint_x^alphatext{y}^text{n}cdotexpleft(xcdottext{y}^{text{n}-2}right)spacetext{d}text{y}spacetext{d}xtag1$$



              Using that (for all $x$):



              $$expleft(xright)=sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}tag2$$



              We can write:



              $$mathcal{I}_text{n}left(alpharight)=int_0^alphaint_x^alphatext{y}^text{n}cdotsum_{text{k}=0}^inftyfrac{left(xcdottext{y}^{text{n}-2}right)^text{k}}{text{k}!}spacetext{d}text{y}spacetext{d}x=$$
              $$int_0^alphaint_x^alphatext{y}^text{n}cdotsum_{text{k}=0}^inftyfrac{x^text{k}cdottext{y}^{text{k}left(text{n}-2right)}}{text{k}!}spacetext{d}text{y}spacetext{d}x=$$
              $$int_0^alphaleft{sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}int_x^alphatext{y}^text{n}cdottext{y}^{text{k}left(text{n}-2right)}spacetext{d}text{y}right}spacetext{d}x=$$
              $$int_0^alphaleft{sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}int_x^alphatext{y}^{text{n}+text{k}left(text{n}-2right)}spacetext{d}text{y}right}spacetext{d}x=$$
              $$int_0^alphaleft{sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}cdotleft[frac{text{y}^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}right]_x^alpharight}spacetext{d}x=$$
              $$int_0^alphaleft{sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}cdotleft(frac{alpha^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}-frac{x^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}right)right}spacetext{d}x=$$
              $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotleft{frac{alpha^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}cdotint_0^alpha x^text{k}spacetext{d}x-frac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotint_0^alpha x^{1+text{n}+text{k}left(text{n}-1right)}spacetext{d}xright}=$$
              $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotleft{frac{alpha^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}cdotfrac{alpha^{1+text{k}}}{1+text{k}}-frac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotfrac{alpha^{1+1+text{n}+text{k}left(text{n}-1right)}}{1+1+text{n}+text{k}left(text{n}-1right)}right}=$$
              $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotleft{frac{alpha^{2+text{n}+text{k}left(text{n}-1right)}}{1+text{n}+text{k}left(text{n}-2right)}cdotfrac{1}{1+text{k}}-frac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotfrac{alpha^{2+text{n}+text{k}left(text{n}-1right)}}{2+text{n}+text{k}left(text{n}-1right)}right}=$$
              $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotfrac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotleft{frac{alpha^{2+text{n}+text{k}left(text{n}-1right)}}{1+text{k}}-frac{alpha^{2+text{n}+text{k}left(text{n}-1right)}}{2+text{n}+text{k}left(text{n}-1right)}right}tag3$$



              When $alpha=1$, we get:



              $$mathcal{I}_text{n}left(1right):=int_0^1int_x^1text{y}^text{n}cdotexpleft(xcdottext{y}^{text{n}-2}right)spacetext{d}text{y}spacetext{d}x=$$
              $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotfrac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotleft{frac{1}{1+text{k}}-frac{1}{2+text{n}+text{k}left(text{n}-1right)}right}=$$
              $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotfrac{1}{1+text{k}}cdotfrac{1}{2+text{n}+text{k}left(text{n}-1right)}tag4$$






              share|cite|improve this answer











              $endgroup$


















                2












                $begingroup$

                Well, solving a much more general problem:



                $$mathcal{I}_text{n}left(alpharight):=int_0^alphaint_x^alphatext{y}^text{n}cdotexpleft(xcdottext{y}^{text{n}-2}right)spacetext{d}text{y}spacetext{d}xtag1$$



                Using that (for all $x$):



                $$expleft(xright)=sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}tag2$$



                We can write:



                $$mathcal{I}_text{n}left(alpharight)=int_0^alphaint_x^alphatext{y}^text{n}cdotsum_{text{k}=0}^inftyfrac{left(xcdottext{y}^{text{n}-2}right)^text{k}}{text{k}!}spacetext{d}text{y}spacetext{d}x=$$
                $$int_0^alphaint_x^alphatext{y}^text{n}cdotsum_{text{k}=0}^inftyfrac{x^text{k}cdottext{y}^{text{k}left(text{n}-2right)}}{text{k}!}spacetext{d}text{y}spacetext{d}x=$$
                $$int_0^alphaleft{sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}int_x^alphatext{y}^text{n}cdottext{y}^{text{k}left(text{n}-2right)}spacetext{d}text{y}right}spacetext{d}x=$$
                $$int_0^alphaleft{sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}int_x^alphatext{y}^{text{n}+text{k}left(text{n}-2right)}spacetext{d}text{y}right}spacetext{d}x=$$
                $$int_0^alphaleft{sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}cdotleft[frac{text{y}^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}right]_x^alpharight}spacetext{d}x=$$
                $$int_0^alphaleft{sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}cdotleft(frac{alpha^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}-frac{x^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}right)right}spacetext{d}x=$$
                $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotleft{frac{alpha^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}cdotint_0^alpha x^text{k}spacetext{d}x-frac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotint_0^alpha x^{1+text{n}+text{k}left(text{n}-1right)}spacetext{d}xright}=$$
                $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotleft{frac{alpha^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}cdotfrac{alpha^{1+text{k}}}{1+text{k}}-frac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotfrac{alpha^{1+1+text{n}+text{k}left(text{n}-1right)}}{1+1+text{n}+text{k}left(text{n}-1right)}right}=$$
                $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotleft{frac{alpha^{2+text{n}+text{k}left(text{n}-1right)}}{1+text{n}+text{k}left(text{n}-2right)}cdotfrac{1}{1+text{k}}-frac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotfrac{alpha^{2+text{n}+text{k}left(text{n}-1right)}}{2+text{n}+text{k}left(text{n}-1right)}right}=$$
                $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotfrac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotleft{frac{alpha^{2+text{n}+text{k}left(text{n}-1right)}}{1+text{k}}-frac{alpha^{2+text{n}+text{k}left(text{n}-1right)}}{2+text{n}+text{k}left(text{n}-1right)}right}tag3$$



                When $alpha=1$, we get:



                $$mathcal{I}_text{n}left(1right):=int_0^1int_x^1text{y}^text{n}cdotexpleft(xcdottext{y}^{text{n}-2}right)spacetext{d}text{y}spacetext{d}x=$$
                $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotfrac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotleft{frac{1}{1+text{k}}-frac{1}{2+text{n}+text{k}left(text{n}-1right)}right}=$$
                $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotfrac{1}{1+text{k}}cdotfrac{1}{2+text{n}+text{k}left(text{n}-1right)}tag4$$






                share|cite|improve this answer











                $endgroup$
















                  2












                  2








                  2





                  $begingroup$

                  Well, solving a much more general problem:



                  $$mathcal{I}_text{n}left(alpharight):=int_0^alphaint_x^alphatext{y}^text{n}cdotexpleft(xcdottext{y}^{text{n}-2}right)spacetext{d}text{y}spacetext{d}xtag1$$



                  Using that (for all $x$):



                  $$expleft(xright)=sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}tag2$$



                  We can write:



                  $$mathcal{I}_text{n}left(alpharight)=int_0^alphaint_x^alphatext{y}^text{n}cdotsum_{text{k}=0}^inftyfrac{left(xcdottext{y}^{text{n}-2}right)^text{k}}{text{k}!}spacetext{d}text{y}spacetext{d}x=$$
                  $$int_0^alphaint_x^alphatext{y}^text{n}cdotsum_{text{k}=0}^inftyfrac{x^text{k}cdottext{y}^{text{k}left(text{n}-2right)}}{text{k}!}spacetext{d}text{y}spacetext{d}x=$$
                  $$int_0^alphaleft{sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}int_x^alphatext{y}^text{n}cdottext{y}^{text{k}left(text{n}-2right)}spacetext{d}text{y}right}spacetext{d}x=$$
                  $$int_0^alphaleft{sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}int_x^alphatext{y}^{text{n}+text{k}left(text{n}-2right)}spacetext{d}text{y}right}spacetext{d}x=$$
                  $$int_0^alphaleft{sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}cdotleft[frac{text{y}^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}right]_x^alpharight}spacetext{d}x=$$
                  $$int_0^alphaleft{sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}cdotleft(frac{alpha^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}-frac{x^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}right)right}spacetext{d}x=$$
                  $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotleft{frac{alpha^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}cdotint_0^alpha x^text{k}spacetext{d}x-frac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotint_0^alpha x^{1+text{n}+text{k}left(text{n}-1right)}spacetext{d}xright}=$$
                  $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotleft{frac{alpha^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}cdotfrac{alpha^{1+text{k}}}{1+text{k}}-frac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotfrac{alpha^{1+1+text{n}+text{k}left(text{n}-1right)}}{1+1+text{n}+text{k}left(text{n}-1right)}right}=$$
                  $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotleft{frac{alpha^{2+text{n}+text{k}left(text{n}-1right)}}{1+text{n}+text{k}left(text{n}-2right)}cdotfrac{1}{1+text{k}}-frac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotfrac{alpha^{2+text{n}+text{k}left(text{n}-1right)}}{2+text{n}+text{k}left(text{n}-1right)}right}=$$
                  $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotfrac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotleft{frac{alpha^{2+text{n}+text{k}left(text{n}-1right)}}{1+text{k}}-frac{alpha^{2+text{n}+text{k}left(text{n}-1right)}}{2+text{n}+text{k}left(text{n}-1right)}right}tag3$$



                  When $alpha=1$, we get:



                  $$mathcal{I}_text{n}left(1right):=int_0^1int_x^1text{y}^text{n}cdotexpleft(xcdottext{y}^{text{n}-2}right)spacetext{d}text{y}spacetext{d}x=$$
                  $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotfrac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotleft{frac{1}{1+text{k}}-frac{1}{2+text{n}+text{k}left(text{n}-1right)}right}=$$
                  $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotfrac{1}{1+text{k}}cdotfrac{1}{2+text{n}+text{k}left(text{n}-1right)}tag4$$






                  share|cite|improve this answer











                  $endgroup$



                  Well, solving a much more general problem:



                  $$mathcal{I}_text{n}left(alpharight):=int_0^alphaint_x^alphatext{y}^text{n}cdotexpleft(xcdottext{y}^{text{n}-2}right)spacetext{d}text{y}spacetext{d}xtag1$$



                  Using that (for all $x$):



                  $$expleft(xright)=sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}tag2$$



                  We can write:



                  $$mathcal{I}_text{n}left(alpharight)=int_0^alphaint_x^alphatext{y}^text{n}cdotsum_{text{k}=0}^inftyfrac{left(xcdottext{y}^{text{n}-2}right)^text{k}}{text{k}!}spacetext{d}text{y}spacetext{d}x=$$
                  $$int_0^alphaint_x^alphatext{y}^text{n}cdotsum_{text{k}=0}^inftyfrac{x^text{k}cdottext{y}^{text{k}left(text{n}-2right)}}{text{k}!}spacetext{d}text{y}spacetext{d}x=$$
                  $$int_0^alphaleft{sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}int_x^alphatext{y}^text{n}cdottext{y}^{text{k}left(text{n}-2right)}spacetext{d}text{y}right}spacetext{d}x=$$
                  $$int_0^alphaleft{sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}int_x^alphatext{y}^{text{n}+text{k}left(text{n}-2right)}spacetext{d}text{y}right}spacetext{d}x=$$
                  $$int_0^alphaleft{sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}cdotleft[frac{text{y}^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}right]_x^alpharight}spacetext{d}x=$$
                  $$int_0^alphaleft{sum_{text{k}=0}^inftyfrac{x^text{k}}{text{k}!}cdotleft(frac{alpha^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}-frac{x^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}right)right}spacetext{d}x=$$
                  $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotleft{frac{alpha^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}cdotint_0^alpha x^text{k}spacetext{d}x-frac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotint_0^alpha x^{1+text{n}+text{k}left(text{n}-1right)}spacetext{d}xright}=$$
                  $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotleft{frac{alpha^{1+text{n}+text{k}left(text{n}-2right)}}{1+text{n}+text{k}left(text{n}-2right)}cdotfrac{alpha^{1+text{k}}}{1+text{k}}-frac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotfrac{alpha^{1+1+text{n}+text{k}left(text{n}-1right)}}{1+1+text{n}+text{k}left(text{n}-1right)}right}=$$
                  $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotleft{frac{alpha^{2+text{n}+text{k}left(text{n}-1right)}}{1+text{n}+text{k}left(text{n}-2right)}cdotfrac{1}{1+text{k}}-frac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotfrac{alpha^{2+text{n}+text{k}left(text{n}-1right)}}{2+text{n}+text{k}left(text{n}-1right)}right}=$$
                  $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotfrac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotleft{frac{alpha^{2+text{n}+text{k}left(text{n}-1right)}}{1+text{k}}-frac{alpha^{2+text{n}+text{k}left(text{n}-1right)}}{2+text{n}+text{k}left(text{n}-1right)}right}tag3$$



                  When $alpha=1$, we get:



                  $$mathcal{I}_text{n}left(1right):=int_0^1int_x^1text{y}^text{n}cdotexpleft(xcdottext{y}^{text{n}-2}right)spacetext{d}text{y}spacetext{d}x=$$
                  $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotfrac{1}{1+text{n}+text{k}left(text{n}-2right)}cdotleft{frac{1}{1+text{k}}-frac{1}{2+text{n}+text{k}left(text{n}-1right)}right}=$$
                  $$sum_{text{k}=0}^inftyfrac{1}{text{k}!}cdotfrac{1}{1+text{k}}cdotfrac{1}{2+text{n}+text{k}left(text{n}-1right)}tag4$$







                  share|cite|improve this answer














                  share|cite|improve this answer



                  share|cite|improve this answer








                  edited Jan 23 at 8:19

























                  answered Jan 6 at 20:52









                  JanJan

                  21.8k31240




                  21.8k31240






























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