How do you factor # 9x^2 + 9x -28#?

Question

1943 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2017-01-20T07:00:46

The answer is #=(3x+7)(3x-4)#

We use

#(a+b)^2=a^2+2ab+b^2#

#a^2-b^2=(a+b)(a-b)#

We complete the squares

#9x^2+9x-28#

#=9(x^2+x)-28#

#=9(x^2+x+1/4)-28-9/4#

#=9(x+1/2)^2-121/4#

#=(3(x+1/2))^2-(11/2)^2#

#=(3(x+1/2)+11/2)(3(x+1/2)-11/2)#

#=(3x+3/2+11/2)(3x+3/2-11/2)#

#=(3x+14/2)(3x-8/2)#

#=(3x+7)(3x-4)#