For what value of x will |adj A| =-12 if A = \(\begin{bmatrix}x^2 & x\\7 & 1 \end{bmatrix}\)?
Answer & explanation
Correct answer: option 1
|adj A| = \( { |A| }^{ n-1 } \)
-12 = \( { |A| }^{ 2-1 } \)
-12 = |A|
-12 = \( { x }^{ 2 } -7x\)
0 = \( { x }^{ 2 } -7x\)+12
0 = (x-3)(x-4)
x= 3 or x=4