If the matrix $\begin{bmatrix}3 & 2a& -5\\-4 & 0 & b\\-5 & 3 & 7\end{bmatrix}$ is symmetric, then the value of (a + b) is :
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 1
$A=\begin{bmatrix}3 & 2a& -5\\-4 & 0 & b\\-5 & 3 & 7\end{bmatrix}$
$A=A^T⇒\begin{bmatrix}3 & -4& -5\\2a & 0 & 3\\-6 & b & 7\end{bmatrix}=\begin{bmatrix}3 & 2a& -5\\-4 & 0 & b\\-5 & 3 & 7\end{bmatrix}$
So on comparison $a=-2,b=3$
$a+b=1$