Well we are doing factoring and I don't quite understand this problem:

Question

(x+1)(x-3)=117

I simplified and got:

x^2-3x+x-3=117
x^2-2x-3=117
x^2-2x-120=0

I split the middle term and got:

x^2-12x+10x-120=0

What should I do next? I have no idea how to finish factoring this...

thanks,
meloney

Answer 1

now you want to factor by "grouping"

x^2-12x+10x-120=0
x(x-12) + 10(x-12) = 0
((x-12)(x+10) = 0
so x= 12 or x = -10

Answer 2

wow I never would have thought of grouping them. Thanks!!!