please slove x3 +15x^2 + 75x+125=0

Question

need slove step by step

Answer 1

x^3+15x^2+75x+125=0=x^3+3*5x^2+3*5^2x+5^3.

This happens to be the expansion of (x+5)^3=0, so x+5=0 and x=-5.

The clue lay in the coefficients having the common factor 5. This suggested that 5 may be involved in finding the root(s). (a+b)^3=a^3+3a^2b+3ab^2+b^3. So when the cubic was broken down into factors, the two factors of 3 stood out.