Pls help me with this question:

if a and b are two square matrices of the same order then (a+b)(a-b) is equal to..............

If A and B are matrices of same order then A + B  = matrix of same order as of A and B 

And A - B = matrix of same order as of A and B

So (A+B)(A-B) = matrix of same order as A and B

$$\begin{gathered} Let A = \left[\begin{array}{cc}2& 4\\ 6& 8\end{array}\right] , B =\left[\begin{array}{cc}5& 7\\ 9& 2\end{array}\right] \\ So A + B = \left[\begin{array}{cc}7& 11\\ 15& 10\end{array}\right] \\ And A -B = \left[\begin{array}{cc}-3& -3\\ -3& 6\end{array}\right] \\ So (A+B )(A-B) =\left[\begin{array}{cc}-54& 45\\ -75& 15\end{array}\right] \end{gathered}$$