Solve this following
Question:

If $\mathrm{A}=\left[\begin{array}{ccc}1 & 2 & 2 \\ 2 & 1 & -2 \\ \mathrm{a} & 2 & \mathrm{~b}\end{array}\right]$ is a matrix satisfying the equation $\mathrm{AA}^{\mathrm{T}}=9 \mathrm{I}$, where $\mathrm{I}$ is $3 \times 3$ identity

matrix, then the ordered pair $(\mathrm{a}, \mathrm{b})$ is equal to:

1. $(2,1)$

2. $(-2,-1)$

3. $(2,-1)$

4. $(-2,1)$

Correct Option: , 2

Solution: