Condition for a Linear Equation System to have non-trivial Solution












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$begingroup$


I have this Theorem in my book:




For a Homogeneous System of $m$ Linear Equations in $n$ unknowns, if $m lt n$, then the system has a non-trivial solution.




I have a confusion about the condition mentioned: Wouldn't it be $n lt m$ the condition for non-trivial solution? It seems to me that $m lt n$ is precisely the case we have either only trivial solution or no solution at all.










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    0












    $begingroup$


    I have this Theorem in my book:




    For a Homogeneous System of $m$ Linear Equations in $n$ unknowns, if $m lt n$, then the system has a non-trivial solution.




    I have a confusion about the condition mentioned: Wouldn't it be $n lt m$ the condition for non-trivial solution? It seems to me that $m lt n$ is precisely the case we have either only trivial solution or no solution at all.










    share|cite|improve this question











    $endgroup$















      0












      0








      0





      $begingroup$


      I have this Theorem in my book:




      For a Homogeneous System of $m$ Linear Equations in $n$ unknowns, if $m lt n$, then the system has a non-trivial solution.




      I have a confusion about the condition mentioned: Wouldn't it be $n lt m$ the condition for non-trivial solution? It seems to me that $m lt n$ is precisely the case we have either only trivial solution or no solution at all.










      share|cite|improve this question











      $endgroup$




      I have this Theorem in my book:




      For a Homogeneous System of $m$ Linear Equations in $n$ unknowns, if $m lt n$, then the system has a non-trivial solution.




      I have a confusion about the condition mentioned: Wouldn't it be $n lt m$ the condition for non-trivial solution? It seems to me that $m lt n$ is precisely the case we have either only trivial solution or no solution at all.







      linear-algebra systems-of-equations






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      share|cite|improve this question













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      edited Jan 15 at 20:58







      freehumorist

















      asked Jan 15 at 20:29









      freehumoristfreehumorist

      351214




      351214






















          2 Answers
          2






          active

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          1












          $begingroup$

          Hint:



          look at.



          $2x=0$ with $m=1 , n=1$



          and



          $2x+y=0$ with $m=1, n=2$



          what is the equation with non trivial ( i.e. not null) solution?






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Thank you, I can see now.
            $endgroup$
            – freehumorist
            Jan 15 at 20:58



















          0












          $begingroup$

          The book's claim is wrong:



          $$begin{cases}x-y=0,\3x+y=0,\x+y=0end{cases}$$ only has a trivial solution.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Sorry for that. That s on me. I falsely copied the hypothesis. Edited.
            $endgroup$
            – freehumorist
            Jan 15 at 20:58












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          2 Answers
          2






          active

          oldest

          votes








          2 Answers
          2






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          1












          $begingroup$

          Hint:



          look at.



          $2x=0$ with $m=1 , n=1$



          and



          $2x+y=0$ with $m=1, n=2$



          what is the equation with non trivial ( i.e. not null) solution?






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Thank you, I can see now.
            $endgroup$
            – freehumorist
            Jan 15 at 20:58
















          1












          $begingroup$

          Hint:



          look at.



          $2x=0$ with $m=1 , n=1$



          and



          $2x+y=0$ with $m=1, n=2$



          what is the equation with non trivial ( i.e. not null) solution?






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Thank you, I can see now.
            $endgroup$
            – freehumorist
            Jan 15 at 20:58














          1












          1








          1





          $begingroup$

          Hint:



          look at.



          $2x=0$ with $m=1 , n=1$



          and



          $2x+y=0$ with $m=1, n=2$



          what is the equation with non trivial ( i.e. not null) solution?






          share|cite|improve this answer









          $endgroup$



          Hint:



          look at.



          $2x=0$ with $m=1 , n=1$



          and



          $2x+y=0$ with $m=1, n=2$



          what is the equation with non trivial ( i.e. not null) solution?







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Jan 15 at 20:35









          Emilio NovatiEmilio Novati

          52.2k43474




          52.2k43474












          • $begingroup$
            Thank you, I can see now.
            $endgroup$
            – freehumorist
            Jan 15 at 20:58


















          • $begingroup$
            Thank you, I can see now.
            $endgroup$
            – freehumorist
            Jan 15 at 20:58
















          $begingroup$
          Thank you, I can see now.
          $endgroup$
          – freehumorist
          Jan 15 at 20:58




          $begingroup$
          Thank you, I can see now.
          $endgroup$
          – freehumorist
          Jan 15 at 20:58











          0












          $begingroup$

          The book's claim is wrong:



          $$begin{cases}x-y=0,\3x+y=0,\x+y=0end{cases}$$ only has a trivial solution.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Sorry for that. That s on me. I falsely copied the hypothesis. Edited.
            $endgroup$
            – freehumorist
            Jan 15 at 20:58
















          0












          $begingroup$

          The book's claim is wrong:



          $$begin{cases}x-y=0,\3x+y=0,\x+y=0end{cases}$$ only has a trivial solution.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Sorry for that. That s on me. I falsely copied the hypothesis. Edited.
            $endgroup$
            – freehumorist
            Jan 15 at 20:58














          0












          0








          0





          $begingroup$

          The book's claim is wrong:



          $$begin{cases}x-y=0,\3x+y=0,\x+y=0end{cases}$$ only has a trivial solution.






          share|cite|improve this answer









          $endgroup$



          The book's claim is wrong:



          $$begin{cases}x-y=0,\3x+y=0,\x+y=0end{cases}$$ only has a trivial solution.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Jan 15 at 20:56









          Yves DaoustYves Daoust

          131k676229




          131k676229












          • $begingroup$
            Sorry for that. That s on me. I falsely copied the hypothesis. Edited.
            $endgroup$
            – freehumorist
            Jan 15 at 20:58


















          • $begingroup$
            Sorry for that. That s on me. I falsely copied the hypothesis. Edited.
            $endgroup$
            – freehumorist
            Jan 15 at 20:58
















          $begingroup$
          Sorry for that. That s on me. I falsely copied the hypothesis. Edited.
          $endgroup$
          – freehumorist
          Jan 15 at 20:58




          $begingroup$
          Sorry for that. That s on me. I falsely copied the hypothesis. Edited.
          $endgroup$
          – freehumorist
          Jan 15 at 20:58


















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