Factorising equations:

Lets look at the example: Factorise 3x+21

In order to factorise this equation, we need to find a common factor of both 3x and 21. For this equation, the common factor is 3 and so this is the number that goes outside the brackets.

We then need to work out how many times 3 goes into 3x and 21. We know that 3x ÷ 3 = x, and 21 ÷ 3 = 7. Therefore, 3x+21 can be factorised to give 3(x+7)

Expanding brackets:

Lets look at the same example but in reverse order: Expand 3(x+7)

This is the opposite of factorising and so now we need to multiply each term inside the brackets by the number outside the brackets.

First we need to multiply 3 by x which gives us 3x.

Then we multiply 3 by 7 which gives us 21.

Our final expansion is: 3x+21

Factorise and solve x^2 -8x=15=0

Related Maths GCSE answers

A) Multiply out 6(n - 2). B) Factorise psquared - 5p

A cylindrical beaker has a height of 16 cm and a diameter at its bottom of 10 cm. What is its volume? Give your answer to 2 decimal places.

Factorising and Expanding Brackets

Fidn the solutions to the quadratic equation: x^2 - 16 = 0