e. If AT-A, then det A = -1.

Algebra and Trigonometry (6th Edition)
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ISBN:9780134463216
Author:Robert F. Blitzer
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ChapterP: Prerequisites: Fundamental Concepts Of Algebra
Section: Chapter Questions
Problem 1MCCP: In Exercises 1-25, simplify the given expression or perform the indicated operation (and simplify,...
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Please answer Exercise 3.2.20 e).
168 Determinants and Diagonalization
Exercise 3.2.19 For each of the matrices in Exercise 2,
find the inverse for those values of c for which it exists.
Exercise 3.2.20 In each case either prove the statement
or give an example showing that it is false:
a. If adj A exists, then A is invertible.
b. If A is invertible and adj A = A-¹, then det A = 1.
c. det (AB) = det (BTA).
d. If det A 0 and AB = AC, then B = C.
e. If AT-A, then det A = -1.
f. If adj A = 0, then A = 0.
g. If A is invertible, then adj A is invertible.
h. If A has a row of zeros, so also does adj A.
i. det (ATA) > 0 for all square matrices A.
j. det (I+A) = 1 + det A.
k. If AB is invertible, then A and B are invertible.
1. If det A = 1, then adj A = A.
m. If A is invertible and det A = d, then adj A =
dA-¹.
Exercise 3.2.21 If A is 2 x 2 and det A = 0, show that
one column of A is a scalar multiple of the other. [Hint:
Definition 2.5 and Part (2) of Theorem 2.4.5.]
Lucanoico 2222 Dind
a. (0, 1),
b. (0, 1),
c. (0, 2),
Exercise 3.2.
det A = 1+ a
and c.
Exercise 3.2.2
a. Show th
only if c
b. Show th
ible, the
Exercise 3.2.27
are integers. SI
implies the oth-
1. A is inve
2. det A =
Transcribed Image Text:168 Determinants and Diagonalization Exercise 3.2.19 For each of the matrices in Exercise 2, find the inverse for those values of c for which it exists. Exercise 3.2.20 In each case either prove the statement or give an example showing that it is false: a. If adj A exists, then A is invertible. b. If A is invertible and adj A = A-¹, then det A = 1. c. det (AB) = det (BTA). d. If det A 0 and AB = AC, then B = C. e. If AT-A, then det A = -1. f. If adj A = 0, then A = 0. g. If A is invertible, then adj A is invertible. h. If A has a row of zeros, so also does adj A. i. det (ATA) > 0 for all square matrices A. j. det (I+A) = 1 + det A. k. If AB is invertible, then A and B are invertible. 1. If det A = 1, then adj A = A. m. If A is invertible and det A = d, then adj A = dA-¹. Exercise 3.2.21 If A is 2 x 2 and det A = 0, show that one column of A is a scalar multiple of the other. [Hint: Definition 2.5 and Part (2) of Theorem 2.4.5.] Lucanoico 2222 Dind a. (0, 1), b. (0, 1), c. (0, 2), Exercise 3.2. det A = 1+ a and c. Exercise 3.2.2 a. Show th only if c b. Show th ible, the Exercise 3.2.27 are integers. SI implies the oth- 1. A is inve 2. det A =
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