Question

If $\left[\begin{array}{cc}x& 3x-y\\ zx+z& 3y-w\end{array}\right]=\left[\begin{array}{cc}3& 2\\ 4& 7\end{array}\right]$, then

• A. $x=3,y=7,z=1,w=14$
• B. $x=3,y=-5,x=-1,w=-4$
• C. $x=3,y=6,z=2,w=7$
• D. None of these

Answer 1

The correct option is A $x=3,y=7,z=1,w=14$

Given that $\left[\begin{array}{cc}x& 3x-y\\ zx+z& 3y-w\end{array}\right]=\left[\begin{array}{cc}3& 2\\ 4& 7\end{array}\right]$
comparing both sides:
$x=3$
$3x-y=2$
$\Rightarrow y=9-2=7$
$zx+z=4$
$\Rightarrow z=\frac{4}{3+1}=1$
$3y-w=7$
$\Rightarrow w=21-7=14$
Ans: A