If A = [(1, 2, 2) (2, 1, -2) (a, 2, b)] is a matrix satisfying the equation AA^T = 9I, where I is the identity matrix of order 3

Question

If A = \(\begin{vmatrix}1&2&2\\2&1&-2\\a&2&b\end{vmatrix}\) is a matrix satisfying the equation AA^T = 9I, where I is the identity matrix of order 3, then the ordered pair (a, b) is equal to ___________ 

A = [(1, 2, 2) (2, 1, -2) (a, 2, b)]

(a) (2, -1) 

(b) (-2, 1) 

(c) (2, 1) 

(d) (-2, -1)

Answer 1

Correct option is : (d) (-2, -1)