Question

Can somebody please help me with question b please?

Answer 1

$\bf A= \begin{bmatrix} -2&0\\1&3 \end{bmatrix}\qquad B= \begin{bmatrix} 1&0&3\\-1&3&0 \end{bmatrix}\\\\ -----------------------------\\\\ AB= \begin{bmatrix} (-2\cdot 1)+(0\cdot -1)&(-2\cdot 0)+(0\cdot 3)&(-2\cdot 3)+(0\cdot 0)\\\\ (1\cdot 1)+(3\cdot -1)&(1\cdot 0)+(3\cdot 3)&(1\cdot 3)+(3\cdot 0) \end{bmatrix}$

as you notice above, is the first-row components from A, multiplying all the columns subsequently on B, and you add the products of that row, that gives you one component on the AB matrix

in the one above, we end up with a 2x3 AB matrix