JEE Main 2014 (Online) 12th AprilQuestion 1
If $A=\begin{bmatrix}1&2&x\\3&-1&2\end{bmatrix}$ and $B=\begin{bmatrix}y\\x\\1\end{bmatrix}$ be such that $AB=\begin{bmatrix}6\\8\end{bmatrix}$, then :
Matrices
Solution
$AB=\begin{bmatrix}y+3x\\3y-x+2\end{bmatrix}=\begin{bmatrix}6\\8\end{bmatrix}$: $y=6-3x$, $18-10x+2=8$, $x=\frac65$, $y=\frac{12}5=2x$.