SOLUTION: Hi. I need help with first factoring and then solving this polynomial: x^3-5x^2-4x+20=0

Algebra ->  Exponential-and-logarithmic-functions -> SOLUTION: Hi. I need help with first factoring and then solving this polynomial: x^3-5x^2-4x+20=0      Log On


   

Question 1174996: Hi. I need help with first factoring and then solving this polynomial:
x^3-5x^2-4x+20=0
Answer by ikleyn(52803) About Me  (Show Source):
You can put this solution on YOUR website!
.

To factor this polynomial, apply the grouping method


    x^3 - 5x^2 - 4x + 20 = (x^3 - 5x^2) - (4x-20) = x^2(x - 5) - 4(x-5) = 

  = (x^2-4)*(x-5) = (x-2)*(x+2)*(x-5).


Factoring is complete.


The roots are  x= -2, 2, 5.

Solved.