a) Suppose the product B¹ B is invertible for some matrix B € Rmxk. Show that B (BTB)¯ is idempotent. b) If A is idempotent, show that Inxn – A is also. c) If A is idempotent, show that Inxn - A is invertible by giving an explicit formula for its inverse. d) Suppose that A is idempotent and that we are given x 0 and X satisfying Ax = Xx. Show that λ = {0, 1}.

Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
Section: Chapter Questions
Problem 1RQ
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A matrix A ∈ R^n×n is called idempotent if it satisfies A^2 = A.

a) Suppose the product \( B^T B \) is invertible for some matrix \( B \in \mathbb{R}^{m \times k} \). Show that \( B \left( B^T B \right)^{-1} B^T \) is idempotent.

b) If \( A \) is idempotent, show that \( I_{n \times n} - A \) is also.

c) If \( A \) is idempotent, show that \( \frac{1}{2} I_{n \times n} - A \) is invertible by giving an explicit formula for its inverse.

d) Suppose that \( A \) is idempotent and that we are given \( x \neq 0 \) and \( \lambda \) satisfying \( Ax = \lambda x \). Show that \( \lambda \in \{0, 1\} \).
Transcribed Image Text:a) Suppose the product \( B^T B \) is invertible for some matrix \( B \in \mathbb{R}^{m \times k} \). Show that \( B \left( B^T B \right)^{-1} B^T \) is idempotent. b) If \( A \) is idempotent, show that \( I_{n \times n} - A \) is also. c) If \( A \) is idempotent, show that \( \frac{1}{2} I_{n \times n} - A \) is invertible by giving an explicit formula for its inverse. d) Suppose that \( A \) is idempotent and that we are given \( x \neq 0 \) and \( \lambda \) satisfying \( Ax = \lambda x \). Show that \( \lambda \in \{0, 1\} \).
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