24. Suppose A is n x n and the equation Ax = b has a solution for each b in R". Explain why A must be invertible. [Hint: Is A row equivalent to I?]

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Chapter2: Second-order Linear Odes
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Ans 24
trivial solution. Explain why A has n pivot columns and A is
row equivalent to I. By Theorem 7, this shows that A must
be invertible. (This exercise and Exercise 24 will be cited in
Section 2.3.)
24. Suppose A is n x n and the equation Ax = b has a solution
for each b in R". Explain why A must be invertible. [Hint: Is
A row equivalent to In?]
Exercises 25 and 26 prove Theorem 4 for A
[ ]
d
25. Show that if ad bc = 0, then the equation Ax = 0 has
more than one solution. Why does this imply that A is not
invertible? [Hint: First, consider a = b = 0. Then, if a and
b
[2]
a
26. Show that if ad - bc #0, the formula for A works.
wom
b are not both zero, consider the vector x =
Transcribed Image Text:trivial solution. Explain why A has n pivot columns and A is row equivalent to I. By Theorem 7, this shows that A must be invertible. (This exercise and Exercise 24 will be cited in Section 2.3.) 24. Suppose A is n x n and the equation Ax = b has a solution for each b in R". Explain why A must be invertible. [Hint: Is A row equivalent to In?] Exercises 25 and 26 prove Theorem 4 for A [ ] d 25. Show that if ad bc = 0, then the equation Ax = 0 has more than one solution. Why does this imply that A is not invertible? [Hint: First, consider a = b = 0. Then, if a and b [2] a 26. Show that if ad - bc #0, the formula for A works. wom b are not both zero, consider the vector x =
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