Question

If $\left[\begin{array}{cc}1& 1\\ -1& 1\end{array}\right]\left[\begin{array}{c}x\\ y\end{array}\right]=\left[\begin{array}{c}2\\ 4\end{array}\right]$ then the values of x and y respectively are

• A. -3, -1
• B. 1,3
• C. 3,1
• D. -1,3

Answer 1

Answer: (D)

Given $\left[\begin{array}{cc}1& 1\\ -1& 1\end{array}\right]\left[\begin{array}{c}x\\ y\end{array}\right]=\left[\begin{array}{c}2\\ 4\end{array}\right]$
$\Rightarrow x+y=2$ and $-x+y=4$
$\Rightarrow x=-1,y=3$