Solve the equation below for x. What is the solution set?

5(x-2)^2=125

Answer : x=-3 or x=7

I know I need to do factoring, just forget how to set it up. I also can't figure out where this -20x+20 came from. Thanks for the assistance.

2 answers

not much factoring here.

5(x-2)^2 = 125
(x-2)^2 = 25
x-2 = ±5

x-2 = +5: x = 7
x-2 = -5: x = -3
as for the -20x+20,

5(x-2)^2 = 5(x^2-4x+4)
= 5x^2-20x+20