LO: Factorise into a single bracket

STARTER: have a go at expanding the brackets below

Mark your answers:

You have been practising expanding brackets or multiplying out brackets.  Today we are doing the reverse - putting things back into brackets, this is called FACTORISING.

First you look for what 'goes into' both parts, put that on the outside of your bracket.

Then see what you need to multiply by up by to get the original things...

eg factorise 12a+8

What goes into both parts? 4, so put 4 outside the bracket

4(         )

4 times what makes 12a?  3a

4 times what makes 8?  2

So we write 12a + 8 = 4(3a + 2)

Similarly for 10b² + 15b

What goes into both parts?  5 and b so write

5b(          )

What do you multiply 5b by to get 10b²?  2b

What do you multiply 5b by to get 15b?  Just 3

So 10b² + 15b = 5b(2b + 3)

You can always check your answers by expanding them

You could check you have got this by trying to reverse the questions you did above - there are some more examples below from the book.