Factorisation Lesson 2

Question 1

Factorise x2 + 10x +16

Answer 1

First:

x2 + 10x + 16

16=1x16
16=2x8

Second:

16=2x8
2+8=10

Finally:

(x +2) (x + 8)

(doesn’t matter which order)

Question 2

Factorise x2 - 2x - 15

Answer 2

First:

-15 = -5 x 3

(The smallest factor must be postive)

Finally:

(x+3) (x-5)

Question 3

Factorise: x2 - 81

Answer 3

First:

x-9
(square root both)

Second:

Since it is -81…

(x + 9) (x - 9)

Question 4

2x2 + 7x + 3

Answer 4

First:

2 x 3 = 6

Second:

6= 1x6

Third:

Seperate expression into two parts…

2x2 + x I 6x + 3

x(2x + 1) I 3(2x + 1)

Finally: (2x + 1) (x + 3)