Do similar matrices have same characteristic equations? [on hold]
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Since similar matrices have same eigenvalues and characteristic polynomials, then they must have the same characteristic equation, right?
linear-algebra matrices eigenvalues-eigenvectors
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put on hold as off-topic by user21820, mrtaurho, Song, Peter Foreman, Lee David Chung Lin 6 hours ago
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$begingroup$
Since similar matrices have same eigenvalues and characteristic polynomials, then they must have the same characteristic equation, right?
linear-algebra matrices eigenvalues-eigenvectors
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put on hold as off-topic by user21820, mrtaurho, Song, Peter Foreman, Lee David Chung Lin 6 hours ago
This question appears to be off-topic. The users who voted to close gave this specific reason:
- "This question is missing context or other details: Please provide additional context, which ideally explains why the question is relevant to you and our community. Some forms of context include: background and motivation, relevant definitions, source, possible strategies, your current progress, why the question is interesting or important, etc." – user21820, mrtaurho, Song, Peter Foreman, Lee David Chung Lin
If this question can be reworded to fit the rules in the help center, please edit the question.
add a comment |
$begingroup$
Since similar matrices have same eigenvalues and characteristic polynomials, then they must have the same characteristic equation, right?
linear-algebra matrices eigenvalues-eigenvectors
$endgroup$
Since similar matrices have same eigenvalues and characteristic polynomials, then they must have the same characteristic equation, right?
linear-algebra matrices eigenvalues-eigenvectors
linear-algebra matrices eigenvalues-eigenvectors
edited 11 hours ago
Rodrigo de Azevedo
13k41960
13k41960
asked 16 hours ago
Samurai BaleSamurai Bale
443
443
put on hold as off-topic by user21820, mrtaurho, Song, Peter Foreman, Lee David Chung Lin 6 hours ago
This question appears to be off-topic. The users who voted to close gave this specific reason:
- "This question is missing context or other details: Please provide additional context, which ideally explains why the question is relevant to you and our community. Some forms of context include: background and motivation, relevant definitions, source, possible strategies, your current progress, why the question is interesting or important, etc." – user21820, mrtaurho, Song, Peter Foreman, Lee David Chung Lin
If this question can be reworded to fit the rules in the help center, please edit the question.
put on hold as off-topic by user21820, mrtaurho, Song, Peter Foreman, Lee David Chung Lin 6 hours ago
This question appears to be off-topic. The users who voted to close gave this specific reason:
- "This question is missing context or other details: Please provide additional context, which ideally explains why the question is relevant to you and our community. Some forms of context include: background and motivation, relevant definitions, source, possible strategies, your current progress, why the question is interesting or important, etc." – user21820, mrtaurho, Song, Peter Foreman, Lee David Chung Lin
If this question can be reworded to fit the rules in the help center, please edit the question.
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2 Answers
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Suppose $A$ and $B$ are square matrices such that $A = P B P^{-1}$ for some invertible matrix $P$. Then
begin{align*}text{charpoly}(A,t) & = det(A - tI)\
& = det(PBP^{-1} - tI)\
& = det(PBP^{-1}-tPP^{-1})\
& = det(P(B-tI)P^{-1})\
& = det(P)det(B - tI) det(P^{-1})\
& = det(P)det(B - tI) frac{1}{det(P)}\
& = det(B-tI)\
& = text{charpoly}(B,t).
end{align*}
This shows that similar matrices have the same characteristic polynomial. Note that this proof relies on several facts. In particular, the determinant is multiplicative.
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Note that $det (lambda I -A) = det S det (lambda I -A) det S^{-1} = det (lambda I - S A S^{-1})$.
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
Suppose $A$ and $B$ are square matrices such that $A = P B P^{-1}$ for some invertible matrix $P$. Then
begin{align*}text{charpoly}(A,t) & = det(A - tI)\
& = det(PBP^{-1} - tI)\
& = det(PBP^{-1}-tPP^{-1})\
& = det(P(B-tI)P^{-1})\
& = det(P)det(B - tI) det(P^{-1})\
& = det(P)det(B - tI) frac{1}{det(P)}\
& = det(B-tI)\
& = text{charpoly}(B,t).
end{align*}
This shows that similar matrices have the same characteristic polynomial. Note that this proof relies on several facts. In particular, the determinant is multiplicative.
$endgroup$
add a comment |
$begingroup$
Suppose $A$ and $B$ are square matrices such that $A = P B P^{-1}$ for some invertible matrix $P$. Then
begin{align*}text{charpoly}(A,t) & = det(A - tI)\
& = det(PBP^{-1} - tI)\
& = det(PBP^{-1}-tPP^{-1})\
& = det(P(B-tI)P^{-1})\
& = det(P)det(B - tI) det(P^{-1})\
& = det(P)det(B - tI) frac{1}{det(P)}\
& = det(B-tI)\
& = text{charpoly}(B,t).
end{align*}
This shows that similar matrices have the same characteristic polynomial. Note that this proof relies on several facts. In particular, the determinant is multiplicative.
$endgroup$
add a comment |
$begingroup$
Suppose $A$ and $B$ are square matrices such that $A = P B P^{-1}$ for some invertible matrix $P$. Then
begin{align*}text{charpoly}(A,t) & = det(A - tI)\
& = det(PBP^{-1} - tI)\
& = det(PBP^{-1}-tPP^{-1})\
& = det(P(B-tI)P^{-1})\
& = det(P)det(B - tI) det(P^{-1})\
& = det(P)det(B - tI) frac{1}{det(P)}\
& = det(B-tI)\
& = text{charpoly}(B,t).
end{align*}
This shows that similar matrices have the same characteristic polynomial. Note that this proof relies on several facts. In particular, the determinant is multiplicative.
$endgroup$
Suppose $A$ and $B$ are square matrices such that $A = P B P^{-1}$ for some invertible matrix $P$. Then
begin{align*}text{charpoly}(A,t) & = det(A - tI)\
& = det(PBP^{-1} - tI)\
& = det(PBP^{-1}-tPP^{-1})\
& = det(P(B-tI)P^{-1})\
& = det(P)det(B - tI) det(P^{-1})\
& = det(P)det(B - tI) frac{1}{det(P)}\
& = det(B-tI)\
& = text{charpoly}(B,t).
end{align*}
This shows that similar matrices have the same characteristic polynomial. Note that this proof relies on several facts. In particular, the determinant is multiplicative.
edited 16 hours ago
J. W. Tanner
3,0121320
3,0121320
answered 16 hours ago
johnny133253johnny133253
459111
459111
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$begingroup$
Note that $det (lambda I -A) = det S det (lambda I -A) det S^{-1} = det (lambda I - S A S^{-1})$.
$endgroup$
add a comment |
$begingroup$
Note that $det (lambda I -A) = det S det (lambda I -A) det S^{-1} = det (lambda I - S A S^{-1})$.
$endgroup$
add a comment |
$begingroup$
Note that $det (lambda I -A) = det S det (lambda I -A) det S^{-1} = det (lambda I - S A S^{-1})$.
$endgroup$
Note that $det (lambda I -A) = det S det (lambda I -A) det S^{-1} = det (lambda I - S A S^{-1})$.
answered 16 hours ago
copper.hatcopper.hat
127k559160
127k559160
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