Question

If B = [(5,2α,1),(0,2,1)(α, 3,-1)] is the inverse of a 3 × 3 matrix A, then the sum of all values of α for which det (A) + 1 = 0, is :

(1) 2  (2) – 1  (3) 0  (4) 1

Answer 1

Correct option (4)  1

Explanation:

If B is inverse of A then

AB = I

det(AB) = det(I)

det(A).det(B) = 1

Given det (A) = –1

 then det (B) = –1