How do you factor #5x^3 -10x^2 - 125x#?

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Answer 1 · 2015-05-23T19:45:32

#5x^3-10x^2-125x#

#=5x(x^2-2x-25)#

#=5x(x^2-2x+1-26)#

#=5x((x-1)^2 - sqrt(26)^2)#

#=5x(x-1-sqrt(26))(x-1+sqrt(26))#

by completing the square and by using the identity #a^2-b^2 = (a-b)(a+b)#

Answer 2 · 2015-05-23T21:55:53

#f(x) = 5x(x^2 - 2x -25)#

The trinomial in parentheses can't be factored because its D = b^2 - 4ac = 4 + 100 = 104 isn't a perfect square.