Question

If $\left[\begin{array}{ccc}1& 2& 4\\ -1& 0& 9\end{array}\right]+A=\left[\begin{array}{ccc}9& -1& 1\\ 4& -2& 3\end{array}\right],$ then $A$ is

• A. $\left[\begin{array}{ccc}3& -8& -3\\ 5& -2& -6\end{array}\right]$
• B. $\left[\begin{array}{ccc}8& -3& -3\\ 5& -2& -6\end{array}\right]$
• C. $\left[\begin{array}{ccc}10& -1& -3\\ 6& -2& -6\end{array}\right]$
• D. $\left[\begin{array}{ccc}6& -3& -3\\ 10& -2& -6\end{array}\right]$

Answer 1

The correct option is B $\left[\begin{array}{ccc}8& -3& -3\\ 5& -2& -6\end{array}\right]$

$\left[\begin{array}{ccc}1& 2& 4\\ -1& 0& 9\end{array}\right]+A=\left[\begin{array}{ccc}9& -1& 1\\ 4& -2& 3\end{array}\right]$

$A=\left[\begin{array}{ccc}9& -1& 1\\ 4& -2& 3\end{array}\right]-\left[\begin{array}{ccc}1& 2& 4\\ -1& 0& 9\end{array}\right]$

$=\left[\begin{array}{ccc}9-1& -1-2& 1-4\\ 4+1& -2-0& 3-9\end{array}\right]$

$A=\left[\begin{array}{ccc}8& -3& -3\\ 5& -2& -6\end{array}\right]$

Hence, $A=\left[\begin{array}{ccc}8& -3& -3\\ 5& -2& -6\end{array}\right]$