GCSE Mathematics/Matrices

Adding/subtracting matrices
When adding or subtracting matrices you should add/subtract numbers in the same position, like this:
 * $$\begin{bmatrix}

1 & 5 \\ 4 & 2 \\ \end{bmatrix} + \begin{bmatrix} 7 & 2 \\ 5 & 3 \\ \end{bmatrix} = \begin{bmatrix} 8 & 7 \\ 9 & 5 \\ \end{bmatrix}$$
 * $$\begin{bmatrix}

7 & 5 \\ 4 & -2 \\ \end{bmatrix} - \begin{bmatrix} -1 & 2 \\ -3 & 5 \\ \end{bmatrix} = \begin{bmatrix} 8 & 3 \\ 7 & -7 \\ \end{bmatrix}$$ Matrices can only be added/subtracted if they are of the same size.

Multiplying matrices
When multiplying matrices by a number, you should multiply all the numbers inside them by that number, for example:
 * $$2\begin{bmatrix}

1 & 3 \\ 4 & 2 \\ \end{bmatrix} = \begin{bmatrix} 2 & 6 \\ 8 & 4 \\ \end{bmatrix}$$