Help with “partial differential equation” definition












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From wikipedia: "PDE is a differential equation that contains beforehand unknown multivariable functions and their partial derivatives".



My dubt is: suppose you have the following variable



$u =u(x_1, x_2)$



where $x_1$ and $x_2$ are independent variables



and a particular physical problem that is modeled with one the following equations:



1) $frac{du}{dx_1}=5$



2) $frac{du}{dx_1}=5*x_1$



3) $frac{du}{dx_1}=5*x_2$



Can this equations be considered as PDE since in those appears only the derivative with respect a one of the dependent variables?










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$endgroup$












  • $begingroup$
    Yes they are. The first equation has solution $5x_1+c$ if u is a function of the single variable $x_1$. It has the solution $5x+f(x_2)$ where f is an arbitrary function of $x_2$ if u depends on $x_1$ and $x_2$.
    $endgroup$
    – Paul
    Jan 18 at 13:49
















0












$begingroup$


From wikipedia: "PDE is a differential equation that contains beforehand unknown multivariable functions and their partial derivatives".



My dubt is: suppose you have the following variable



$u =u(x_1, x_2)$



where $x_1$ and $x_2$ are independent variables



and a particular physical problem that is modeled with one the following equations:



1) $frac{du}{dx_1}=5$



2) $frac{du}{dx_1}=5*x_1$



3) $frac{du}{dx_1}=5*x_2$



Can this equations be considered as PDE since in those appears only the derivative with respect a one of the dependent variables?










share|cite|improve this question









$endgroup$












  • $begingroup$
    Yes they are. The first equation has solution $5x_1+c$ if u is a function of the single variable $x_1$. It has the solution $5x+f(x_2)$ where f is an arbitrary function of $x_2$ if u depends on $x_1$ and $x_2$.
    $endgroup$
    – Paul
    Jan 18 at 13:49














0












0








0





$begingroup$


From wikipedia: "PDE is a differential equation that contains beforehand unknown multivariable functions and their partial derivatives".



My dubt is: suppose you have the following variable



$u =u(x_1, x_2)$



where $x_1$ and $x_2$ are independent variables



and a particular physical problem that is modeled with one the following equations:



1) $frac{du}{dx_1}=5$



2) $frac{du}{dx_1}=5*x_1$



3) $frac{du}{dx_1}=5*x_2$



Can this equations be considered as PDE since in those appears only the derivative with respect a one of the dependent variables?










share|cite|improve this question









$endgroup$




From wikipedia: "PDE is a differential equation that contains beforehand unknown multivariable functions and their partial derivatives".



My dubt is: suppose you have the following variable



$u =u(x_1, x_2)$



where $x_1$ and $x_2$ are independent variables



and a particular physical problem that is modeled with one the following equations:



1) $frac{du}{dx_1}=5$



2) $frac{du}{dx_1}=5*x_1$



3) $frac{du}{dx_1}=5*x_2$



Can this equations be considered as PDE since in those appears only the derivative with respect a one of the dependent variables?







terminology






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Jan 18 at 13:45









user2235427user2235427

1083




1083












  • $begingroup$
    Yes they are. The first equation has solution $5x_1+c$ if u is a function of the single variable $x_1$. It has the solution $5x+f(x_2)$ where f is an arbitrary function of $x_2$ if u depends on $x_1$ and $x_2$.
    $endgroup$
    – Paul
    Jan 18 at 13:49


















  • $begingroup$
    Yes they are. The first equation has solution $5x_1+c$ if u is a function of the single variable $x_1$. It has the solution $5x+f(x_2)$ where f is an arbitrary function of $x_2$ if u depends on $x_1$ and $x_2$.
    $endgroup$
    – Paul
    Jan 18 at 13:49
















$begingroup$
Yes they are. The first equation has solution $5x_1+c$ if u is a function of the single variable $x_1$. It has the solution $5x+f(x_2)$ where f is an arbitrary function of $x_2$ if u depends on $x_1$ and $x_2$.
$endgroup$
– Paul
Jan 18 at 13:49




$begingroup$
Yes they are. The first equation has solution $5x_1+c$ if u is a function of the single variable $x_1$. It has the solution $5x+f(x_2)$ where f is an arbitrary function of $x_2$ if u depends on $x_1$ and $x_2$.
$endgroup$
– Paul
Jan 18 at 13:49










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