(a) Suppose that A and B are square matrices of the same size. Prove that the (A + B)² = A² + 2AB + B² is satisfied if and only if A and B commute. (Note that you are being asked for a general proof. It is not enough to just choose two specific matrices.) Exercise 3. condition

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ChapterP: Prerequisites: Fundamental Concepts Of Algebra
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(a) Suppose that A and B are square matrices of the same size. Prove that the
(A + B)² = A² + 2AB + B²
is satisfied if and only if A and B commute. (Note that you are being asked for a general
proof. It is not enough to just choose two specific matrices.)
(b) Suppose that A is a square matrix with the property that
A³ = 0
Exercise 3.
condition
(here "O" means the zero matrix of the same size as A). Prove that the matrix I + A is
invertible, and that its inverse is given by
(I + A)−¹ = I − A + A².
(Note that you cannot assume anything about A other than the condition A³ = 0.)
(c) Suppose that A is an invertible matrix. Prove that AT is also invertible, and that its inverse
is given by
(AT)−¹ = (A¯¹)T .
(Hint: you need to verify the condition in the definition of the "inverse" of a matrix. The
property (AB)T = BT AT might be useful.)
Transcribed Image Text:(a) Suppose that A and B are square matrices of the same size. Prove that the (A + B)² = A² + 2AB + B² is satisfied if and only if A and B commute. (Note that you are being asked for a general proof. It is not enough to just choose two specific matrices.) (b) Suppose that A is a square matrix with the property that A³ = 0 Exercise 3. condition (here "O" means the zero matrix of the same size as A). Prove that the matrix I + A is invertible, and that its inverse is given by (I + A)−¹ = I − A + A². (Note that you cannot assume anything about A other than the condition A³ = 0.) (c) Suppose that A is an invertible matrix. Prove that AT is also invertible, and that its inverse is given by (AT)−¹ = (A¯¹)T . (Hint: you need to verify the condition in the definition of the "inverse" of a matrix. The property (AB)T = BT AT might be useful.)
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