Please show me the workings of this no.2?

Mar 7, 2018

This is direct scalar multiplication and then subtraction of matrices.

Explanation:

Scalar multiplication of matrices simply means that each element in the matrix is multiplied by the constant. So, each element in A will be multiplied by 2.

Then, matrix subtraction (and addition) is performed by element by element subtraction.

So, in this case, 2(-8) = -16. Then, you will subtract the 1 in the upper right corner of B to give -16 - 1 = -17.

So, a = 17

Mar 7, 2018

$- 17$

Explanation:

Given that $A = \left(\begin{matrix}2 & 1 & \textcolor{g r e e n}{- 8} \\ - 9 & 4 & 7 \\ - 1 & 9 & 3 \\ 1 & 4 & 1\end{matrix}\right)$

Then $2 A = \left(\begin{matrix}4 & 2 & \textcolor{g r e e n}{- 16} \\ - 18 & 8 & 14 \\ - 2 & 18 & 6 \\ 2 & 8 & 1\end{matrix}\right)$

Given that $B = \left(\begin{matrix}3 & 3 & \textcolor{red}{1} \\ 3 & - 3 & - 3 \\ 7 & - 2 & - 4 \\ - 9 & 1 & - 7\end{matrix}\right)$

So for the element $a$ we have:

$\textcolor{g r e e n}{\textcolor{w h i t e}{\text{d}} 2 A} - \textcolor{red}{B}$

$\textcolor{g r e e n}{- 16} - \textcolor{red}{1} = - 17$