# If 12 2 A 21 2 a2 b é ù ê ú = – ê ú ê ú ë û is a matrix satisfying the equation AAT = 9I, where I is 3 × 3 identity matrix, then the ordered pair (a, b) is equal to:

Question:

If $A=\left[\begin{array}{ccc}1 & 2 & 2 \\ 2 & 1 & -2 \\ a & 2 & b\end{array}\right]$ 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 $(a, b)$ is equal to:

1. $(2,1)$

2. $(-2,-1)$

3. $(2,-1)$

4. $(-2,1)$

Correct Option: 2

JEE Main Previous Year 1 Question of JEE Main from Mathematics Inverse Trigonometric Functions chapter.
JEE Main Previous Year 2015

Solution:

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