Question

IfA equals a 2 by 2 matrix: row one is 1, 4 and row two is 5, 2 find -2A.

Answer 1

"scalar" multiplication is very straightforward,


`\bf A= \begin{bmatrix} 1&4\\ 5&2 \end{bmatrix}\qquad -2A=\begin{bmatrix} -2\cdot 1&-2\cdot 4\\ -2\cdot 5&-2\cdot 2 \end{bmatrix}\implies \begin{bmatrix} -2&-8\\ -10&-4 \end{bmatrix}`