# How do you factor the expression 10x^2 - 90?

Feb 6, 2016

10(x-3)(x+3)

#### Explanation:

in the expression $10 {x}^{2} - 90$

there is a 'common factor' of 10

hence $10 {x}^{2} - 90 = 10 \left({x}^{2} - 9\right)$

inside the bracket there is a 'difference of squares '

In general : ${a}^{2} - {b}^{2} = \left(a - b\right) \left(a + b\right)$

$\Rightarrow 10 {x}^{2} - 90 = 10 \left(x - 3\right) \left(x + 3\right)$