Prove that any eigenvectors of $A^-1$ must be in some subspace of $adj(A)$

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Prove that any eigenvectors of $A^-1$ must be in some subspace of $adj(A)$



Since $A^-1$=$frac1detAajdA$, so if $lambda$ is eigenvalue of $A^-1$ so it exist $xnot=0$ such that $A^-1x=lambda x$ then $frac1detAajdAx=lambda x$ since $frac1det$ is some scalar then $adjAx=detAlambda x$ and if I put $lambda´=detAlambda$ then $adjAx=lambda^´ x$, so they have the same eigenvectors, I think that is easy way to show but what you think?










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  • What's "some subspace of $adj(A)$ means?
    – Vim
    Sep 8 at 9:12










  • I think that I need to write eigensubspace
    – Marko Å korić
    Sep 8 at 9:14






  • 1




    As you have noted $A^-1$ is just a non-zero multiple of $textadj(A)$ so they trivially have the same eigenvectors don't they?
    – Vim
    Sep 8 at 9:15










  • Yes you are right
    – Marko Å korić
    Sep 8 at 9:17














up vote
3
down vote

favorite












Prove that any eigenvectors of $A^-1$ must be in some subspace of $adj(A)$



Since $A^-1$=$frac1detAajdA$, so if $lambda$ is eigenvalue of $A^-1$ so it exist $xnot=0$ such that $A^-1x=lambda x$ then $frac1detAajdAx=lambda x$ since $frac1det$ is some scalar then $adjAx=detAlambda x$ and if I put $lambda´=detAlambda$ then $adjAx=lambda^´ x$, so they have the same eigenvectors, I think that is easy way to show but what you think?










share|cite|improve this question























  • What's "some subspace of $adj(A)$ means?
    – Vim
    Sep 8 at 9:12










  • I think that I need to write eigensubspace
    – Marko Å korić
    Sep 8 at 9:14






  • 1




    As you have noted $A^-1$ is just a non-zero multiple of $textadj(A)$ so they trivially have the same eigenvectors don't they?
    – Vim
    Sep 8 at 9:15










  • Yes you are right
    – Marko Å korić
    Sep 8 at 9:17












up vote
3
down vote

favorite









up vote
3
down vote

favorite











Prove that any eigenvectors of $A^-1$ must be in some subspace of $adj(A)$



Since $A^-1$=$frac1detAajdA$, so if $lambda$ is eigenvalue of $A^-1$ so it exist $xnot=0$ such that $A^-1x=lambda x$ then $frac1detAajdAx=lambda x$ since $frac1det$ is some scalar then $adjAx=detAlambda x$ and if I put $lambda´=detAlambda$ then $adjAx=lambda^´ x$, so they have the same eigenvectors, I think that is easy way to show but what you think?










share|cite|improve this question















Prove that any eigenvectors of $A^-1$ must be in some subspace of $adj(A)$



Since $A^-1$=$frac1detAajdA$, so if $lambda$ is eigenvalue of $A^-1$ so it exist $xnot=0$ such that $A^-1x=lambda x$ then $frac1detAajdAx=lambda x$ since $frac1det$ is some scalar then $adjAx=detAlambda x$ and if I put $lambda´=detAlambda$ then $adjAx=lambda^´ x$, so they have the same eigenvectors, I think that is easy way to show but what you think?







linear-algebra matrices eigenvalues-eigenvectors






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share|cite|improve this question













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edited Sep 8 at 8:33

























asked Sep 8 at 8:24









Marko Škorić

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4008











  • What's "some subspace of $adj(A)$ means?
    – Vim
    Sep 8 at 9:12










  • I think that I need to write eigensubspace
    – Marko Å korić
    Sep 8 at 9:14






  • 1




    As you have noted $A^-1$ is just a non-zero multiple of $textadj(A)$ so they trivially have the same eigenvectors don't they?
    – Vim
    Sep 8 at 9:15










  • Yes you are right
    – Marko Å korić
    Sep 8 at 9:17
















  • What's "some subspace of $adj(A)$ means?
    – Vim
    Sep 8 at 9:12










  • I think that I need to write eigensubspace
    – Marko Å korić
    Sep 8 at 9:14






  • 1




    As you have noted $A^-1$ is just a non-zero multiple of $textadj(A)$ so they trivially have the same eigenvectors don't they?
    – Vim
    Sep 8 at 9:15










  • Yes you are right
    – Marko Å korić
    Sep 8 at 9:17















What's "some subspace of $adj(A)$ means?
– Vim
Sep 8 at 9:12




What's "some subspace of $adj(A)$ means?
– Vim
Sep 8 at 9:12












I think that I need to write eigensubspace
– Marko Å korić
Sep 8 at 9:14




I think that I need to write eigensubspace
– Marko Å korić
Sep 8 at 9:14




1




1




As you have noted $A^-1$ is just a non-zero multiple of $textadj(A)$ so they trivially have the same eigenvectors don't they?
– Vim
Sep 8 at 9:15




As you have noted $A^-1$ is just a non-zero multiple of $textadj(A)$ so they trivially have the same eigenvectors don't they?
– Vim
Sep 8 at 9:15












Yes you are right
– Marko Å korić
Sep 8 at 9:17




Yes you are right
– Marko Å korić
Sep 8 at 9:17















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