# 7.3 A factorising trinomials

Invoegen plattegrond op niveau
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Slide 1: Slide
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This lesson contains 17 slides, with interactive quizzes and text slides.

Lesson duration is: 50 min

## Items in this lesson

Invoegen plattegrond op niveau

#### Slide 1 -Slide

Invoegen plattegrond op niveau

#### Slide 2 -Slide

Today
You are able to factorise trinomials using the product-sum method.

#### Slide 3 -Slide

Find two numbers of which the product is 15 and the sum 8.

#### Slide 4 -Open question

Find two numbers of which the product is -20 and the sum 8.

#### Slide 5 -Open question

Expand the brackets:
(x+2)(x+7)

#### Slide 6 -Open question

We've just seen that

Can you find a relation between 2, 7 and 9, 14?

This relation is always there.
We can use this relation to factorise trinomials.
(x+2)(x+7)=x2+9x+14

#### Slide 7 -Slide

To factorise

we need two numbers which give +30 when multiplied and +13 when added.

Which two numbers do we need?
There's always just one solution.
x2+13x+30

#### Slide 8 -Slide

To factorise

we need two numbers which give +30 when multiplied and +13 when added.

It's 3 and 10, so
x2+13x+30
x2+13x+30=(x+3)(x+10)

#### Slide 9 -Slide

Three more examples:
x25x50
x2+x6
x2+3x4

#### Slide 10 -Slide

Three more examples:
x25x50
x2+x6
x2+3x4=(x+4)(x1)

#### Slide 11 -Slide

Three more examples:
x25x50
x2+x6=(x+3)(x2)
x2+3x4=(x+4)(x1)

#### Slide 12 -Slide

Three more examples:
x25x50=(x10)(x+5)
x2+x6=(x+3)(x2)
x2+3x4=(x+4)(x1)

Factorise:
x2+6x27
A
(x + 3)(x + 9)
B
(x - 9)(x + 3)
C
(x - 3)(x + 9)
D
(x + 9)(x - 3)

Factorise:
x2+11x+10

Factorise:
x2+2x+1