How do you factor (p-5)^3+125(p5)3+125?

1 Answer
Jan 23, 2016

p(p^2-15p+75)p(p215p+75)

Explanation:

The sum of cubes identity can be written:

a^3+b^3=(a+b)(a^2-ab+b^2)a3+b3=(a+b)(a2ab+b2)

Here, we have

(p-5)^3+125(p5)3+125

=(p-5)^3+5^3=(p5)3+53

=((p-5)+5)((p-5)^2-(p-5)(5)+5^2)=((p5)+5)((p5)2(p5)(5)+52)

=p(p^2-10p+25-5p+25+25)=p(p210p+255p+25+25)

=p(p^2-15p+75)=p(p215p+75)

The internal quadratic p^2-15p+75p215p+75 cannot be factored without using complex numbers.