Let a be a matrix of order 3, | a | = 0.5, find | (2a) ^ (- 1) - 5A * | =? My solution is as follows: The original formula = | - 4A * | according to | AA * | = | - a | - e |, then | - A * | = | - a | ^ 2 = 0.25 So the above formula = - 1, but the answer is - 2?

Let a be a matrix of order 3, | a | = 0.5, find | (2a) ^ (- 1) - 5A * | =? My solution is as follows: The original formula = | - 4A * | according to | AA * | = | - a | - e |, then | - A * | = | - a | ^ 2 = 0.25 So the above formula = - 1, but the answer is - 2?

In your way of thinking
A^-1 = 2A*
|(2A)^(-1)-5A*|
= | (1/2)2A* - 5A*|
= | -4 A*|
= (-4)^3 |A*|
= (-4)^3 |A|^(3-1)
= (-4)^3 * (1/4)
= -16.
How could the answer be - 2