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:

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