SOLUTION: 4x^3 − 20x^2 − 25x + 125 = 0 I started out by trying to factor out an x. So I'm at x(4x^2 - 20x - 25) +125 = 0 Where do i go from here?

Algebra ->  Complex Numbers Imaginary Numbers Solvers and Lesson -> SOLUTION: 4x^3 − 20x^2 − 25x + 125 = 0 I started out by trying to factor out an x. So I'm at x(4x^2 - 20x - 25) +125 = 0 Where do i go from here?      Log On


   

Question 645048: 4x^3 − 20x^2 − 25x + 125 = 0
I started out by trying to factor out an x.
So I'm at x(4x^2 - 20x - 25) +125 = 0
Where do i go from here?
Answer by kekegeter (97) About Me  (Show Source):
You can put this solution on YOUR website!
4x^3 - 20x^2- 25x + 125 =0
4x^2(x-5) +5^2 (-x+5) =0
(x-5)(4x^2-25) =0
x-5= 0
4x^2-25=0
x=5
4x^2 = 25
x^2=5^2/2^2
x=5/2
(x^2)1/2 = -(5^2/2^2)^1/2
x= -(5^2)^1/2/ (2^2)^1/2
x= -5/2
x 5, 5/2, -5/2