1.

Find matrices A and B, if A + B = \(\begin{bmatrix}1&0 & 2 \\[0.3em]5& 4 & -6\\[0.3em]7 & 3& 8\end{bmatrix}\) and A - B = \(\begin{bmatrix}-5&-4 & 8 \\[0.3em]11& 2 & 0\\[0.3em]-1 & 7& 4\end{bmatrix}.\) A + B = [(1,0,2)(5,4,-6)(7,3,8)]A - B = [(-5,-4,8)(11,2,0)(-1,7,4)].

Answer»

Add (A + B) and (A - B)

We get (A + B) + (A - B) = \(\begin{bmatrix}1& 0& 2 \\[0.3em]5 & 4 &-6 \\[0.3em]7 & 3 & 8\end{bmatrix}\) + \(\begin{bmatrix}-5& -4& 8 \\[0.3em]11 & 2 &0 \\[0.3em]-1 & 7 & 4\end{bmatrix}\)

2A = \(\begin{bmatrix}-4& -4& 10 \\[0.3em]16 & 6 &-6 \\[0.3em]6 & 10 & 12\end{bmatrix}\)

A = \(\begin{bmatrix}-2& -2& 5 \\[0.3em]8 & 3 &-3 \\[0.3em]3 & 5 & 6\end{bmatrix}\)

Now Subtract (A - B) from (A + B)

(A + B) - (A - B) = \(\begin{bmatrix}1& 0& 2 \\[0.3em]5 & 4 &-6\\[0.3em]7 & 3& 8\end{bmatrix}\) - \(\begin{bmatrix}-5& -4& 8 \\[0.3em]11 & 2 &0\\[0.3em]-1 & 7& 4\end{bmatrix}\) 

(2B) = \(\begin{bmatrix}6& 4& -6 \\[0.3em]-6 & 2 &-6\\[0.3em]8 & -4& 4\end{bmatrix}\)

B = \(\begin{bmatrix}3& 2& -3 \\[0.3em]-3 & 1 &-3\\[0.3em]4 & -2&2\end{bmatrix}\)

Conclusion: A = \(\begin{bmatrix}-2& -2&5 \\[0.3em]8 & 3 &-3\\[0.3em]3 & 5&6\end{bmatrix},\) B = \(\begin{bmatrix}3& 2&-3 \\[0.3em]-3 & 1 &-3\\[0.3em]4 & -2&2\end{bmatrix}\) 



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