Factorisation

By the end of the lesson you will be able to:

• Factorise quadratic expressions(trinomials) of the form: ax2+bx+c

Factorise fully:

Factorise fully:

Let's try to factorise  

Which two terms multiply to make             ?

2x2+7x+5(            ) (            )

2x2

(            ) (            )

Now, to make the :5(            ) (            )

2x   x 

2x   x +1  +5

Let's expand: 2x2+10x+x+52x2+11x+5

(            ) (            )2x   x +1  +5We have to swap around the 1 and the 5

Now, expand again:

Always expand to check !!!!!!

Factorise: 3x2+16x+21(            ) (            )

List the factors of 21:

so it could be:

(3x +7) ( x + 3)or(3x +3) ( x + 7)

Expand to see which is the correct one. So

3x2+16x+21  = (3x +7) ( x + 3)

Let's try to factorise 3x2+13x­10(            ) (            )

List the factors of -10:

The best way to find the correct pair is trial and improvement

Now even worse! 4x2­4x­3

Which two terms multiply to make ?4x2

It could be:

or(4x     )  ( x         )  (2x      )   ( 2x       )

List the factors of -3:

Now try the different possibilities until you find the correct one

Factorise: 4x2 ­25

solve worksheet "Factorisation " Ex D2

2 x3 ­ 11 x2 + 5x=

At the end of the lesson:

Factorise: