7. Recall the following statement from class: If A and B are similar matrices, then A and B have the same eigenvalues, each occurring with the same algebraic and geometric multiplicities. In this problem, we will complete the proof of this statement by showing that if A is an eigen- value of A (and therefore also of B), then the geometric multiplicity of A as an eigenvalue of A must equal the geometric multiplicity of A as an eigenvalue of B. Suppose B = s-1AS, where A, B, and S are all n x n matrices. Show the (a) following two facts: (i) if v is in ker(B), then Sv is in ker(A). (ii) if w is in ker(A), then S-lw is in ker(B). Let v1, V2,..., Vm be a basis of ker(B). Show that the vectors Sv1, Sv2, Svm, which (by part (a)) are in ker(A), are linearly independent. (b) ... (Hint: Start by considering a nontrivial relation c1(Sv1)+c2(Sv2)+·· What happens if you multiply both sides of this relation by S-1?) ...+cm(Svm) = 0. (c) Show that the vectors Sv1, Sv2, ., Sv m span ker(A). .... (Hint: Let w be a vector in ker(A). What can you say about S-lw?) (d) dim ker(A) Combine (b) and (c) to show that if A and B are similar matrices, then = dim ker(B).

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Chapter2: Second-order Linear Odes
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7. Recall the following statement from class:
If A and B are similar matrices, then A and B have the same eigenvalues, each
occurring with the same algebraic and geometric multiplicities.
In this problem, we will complete the proof of this statement by showing that if A is an eigen-
value of A (and therefore also of B), then the geometric multiplicity of A as an eigenvalue
of A must equal the geometric multiplicity of A as an eigenvalue of B.
Suppose B = s-1AS, where A, B, and S are all n x n matrices. Show the
(a)
following two facts:
(i) if v is in ker(B), then Sv is in ker(A).
(ii) if w is in ker(A), then S-w is in ker(B).
Let v1, V2, . .., Vm be a basis of ker(B). Show that the vectors Sv1, Sv2,
Svm, which (by part (a)) are in ker(A), are linearly independent.
(b)
....
(Hint: Start by considering a nontrivial relation c1(Sv1)+c2(Sv2)+· ·+cm(Svm) = 0.
What happens if you multiply both sides of this relation by S-1?)
(c)
Show that the vectors Sv1, Sv2, ., Sv m span ker(A).
(Hint: Let w be a vector in ker(A). What can you say about S-lw?)
(d)
dim ker(A)
Combine (b) and (c) to show that if A and B are similar matrices, then
= dim ker(B).
(e)
Show that if A and B are similar, then the matrices A – XIn and B – XIn
are similar as well.
(Hint: Take another look at the proof given in class that similar matrices have the
same characteristic polynomial.)
(f)
of A (and therefore also of B), then the geometric multiplicity of A as an eigenvalue of
A must equal the geometric multiplicity of as an eigenvalue of B.
Use your answers to the previous parts to conclude that if is an eigenvalue
Transcribed Image Text:7. Recall the following statement from class: If A and B are similar matrices, then A and B have the same eigenvalues, each occurring with the same algebraic and geometric multiplicities. In this problem, we will complete the proof of this statement by showing that if A is an eigen- value of A (and therefore also of B), then the geometric multiplicity of A as an eigenvalue of A must equal the geometric multiplicity of A as an eigenvalue of B. Suppose B = s-1AS, where A, B, and S are all n x n matrices. Show the (a) following two facts: (i) if v is in ker(B), then Sv is in ker(A). (ii) if w is in ker(A), then S-w is in ker(B). Let v1, V2, . .., Vm be a basis of ker(B). Show that the vectors Sv1, Sv2, Svm, which (by part (a)) are in ker(A), are linearly independent. (b) .... (Hint: Start by considering a nontrivial relation c1(Sv1)+c2(Sv2)+· ·+cm(Svm) = 0. What happens if you multiply both sides of this relation by S-1?) (c) Show that the vectors Sv1, Sv2, ., Sv m span ker(A). (Hint: Let w be a vector in ker(A). What can you say about S-lw?) (d) dim ker(A) Combine (b) and (c) to show that if A and B are similar matrices, then = dim ker(B). (e) Show that if A and B are similar, then the matrices A – XIn and B – XIn are similar as well. (Hint: Take another look at the proof given in class that similar matrices have the same characteristic polynomial.) (f) of A (and therefore also of B), then the geometric multiplicity of A as an eigenvalue of A must equal the geometric multiplicity of as an eigenvalue of B. Use your answers to the previous parts to conclude that if is an eigenvalue
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