Question

If A=$\left[\begin{array}{c}1\\ -2\end{array}\right],B=\left[\begin{array}{c}2\\ 2\end{array}\right]andC=\left[\begin{array}{c}-1\\ 2\end{array}\right]$, find 2A+B-5C

Answer 1

$2A+B-5C=2\left[\begin{array}{c}1\\ -2\end{array}\right]+\left[\begin{array}{c}2\\ 2\end{array}\right]-5\left[\begin{array}{c}-1\\ 2\end{array}\right]$

$=\left[\begin{array}{c}2\\ -4\end{array}\right]+\left[\begin{array}{c}2\\ 2\end{array}\right]-\left[\begin{array}{c}-5\\ 10\end{array}\right]$

$=\left[\begin{array}{c}2+2-(-5)\\ -4+2-10\end{array}\right]$

$=\left[\begin{array}{c}9\\ -12\end{array}\right]$