[SPLIT] Please do this for me: If A = 2 3 find A -7A = 21

[Hilmatjie]

please do this for me
if A= 2 3 find A-7A=21
4 5

 

[soroban]

Hello, Hilmatjie!

Please state the original problem.
As given, it makes no sense.

\(\displaystyle \text{If }A= \begin{bmatrix}2&3\\ 4&5\end{bmatrix},\,\text{ find }A-7A\:=\:21\)

We have: .\(\displaystyle A - 7A \:=\:21 \quad\Rightarrow\quad -6A \,=\,21 \quad\Rightarrow\quad A \,=\,-\frac{7}{2}\)
What does that have to do with the matrix?


We have: .\(\displaystyle \text{-}6A \:=\:21 \quad\Rightarrow\quad \text{-}6\begin{bmatrix}2&3\\4&5\end{bmatrix} \:=\:21 \quad\Rightarrow\quad \begin{bmatrix}\text{-}12&\text{-}18 \\ \text{-}24&\text{-}30\end{bmatrix} \:=\:21\)
How can a matrix equal a scalar?