# How do you factor #7x^2-28 #?

##### 2 Answers

Mar 29, 2017

#### Answer:

#### Explanation:

There is a

#color(blue)"common factor"# of 7 in both terms which can be taken out.

#rArr7(x^2-4)tocolor(red)((1))#

#x^2-4" is a " color(blue)"difference of squares"# which is factorised in general as follows.

#color(red)(bar(ul(|color(white)(2/2)color(black)(a^2-b^2=(a-b)(a+b))color(white)(2/2)|)))#

#"here " a=x" and " b=2#

#rArrx^2-4=(x-2)(x+2)# going back to

#color(red)((1))#

#rArr7x^2-28=7(x-2)(x+2)#

Mar 29, 2017

#### Answer:

#### Explanation:

Always look for a common factor first.

It is

The expression has 3 factors