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