Find all values of k so that

Question

|k + 1 4| -I2
|3 k - 3|

is invertible

inside the "|" is a matrice. subtract I2 from that

Answer 1

Your use of spaces makes things look ambiguous. I assume that you meant
(k+1 4)
(3 k-3)
If so, then you just need a nonzero determinant. Thus,
k(k-1) - 12 ≠ 0
k^2 - k - 12 ≠ 0
(k-4)(k+3) ≠ 0
k ≠ 4 or -3

and the singular is "matrix" not "matrice"
just like vertex

Answer 2

rats. my bad. The determinant is
k(k-4) - 12 = k^2 - 4k - 12
So factor that instead.