Chapter 6: Q25E (page 309)
25. If the determinant of a square matrix is -1, then Amust be an orthogonal matrix.
Short Answer
The given statement is false.
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Chapter 6: Q25E (page 309)
25. If the determinant of a square matrix is -1, then Amust be an orthogonal matrix.
The given statement is false.
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Consider a 4x4 matrix A with rows . If det(A) = 8, find the determinants in Exercises 11 through 16.
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Find the determinants of the linear transformations in Exercises 17 through 28.
17.
IfA is a matrix whose entries are all 1 or -1 , then must be divisible by 8 (i.e., for some integer k).
Question: Let A and B be 2 x 2 matrices with integer entries such that A,A+B,A+2B,A+3B, and A+4B are all invertible matrices whose inverses have integer entries. Show that A+5B is invertible and that it’s inverse has integer entries. This question was in the William Lowell Putnam Mathematical Competition in 1994. Hint: Consider the function F(t)=(det(A+tB))2 -1. Shows that this is a polynomial; what can you say about its degree? Find the values f(0), f(1), f(2), f(3), f(4),using Exercise 53. Now you can determine f(t) by using a familiar result: If a polynomial f(t) of degree <m has more than m zeros, then f(t)=0 for all t.
Which of the following functions F of are linear in both columns? Which are linear in both rows? Which are alternating on the columns?
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