Answer
$(x +5)(x^2 -5x +25)$
Work Step by Step
Since $x^3+125$ is a sum of the two cubes $x^3$ and $5^3$, then by making use of the sum of two cubes
$$a^3 + b^3 = (a + b)(a^2 - ab + b^2),$$
we have
\begin{align*}
x^3 +125&=x^3+5^3\\
&= (x +5)(x^2 -5x + 5^2)\\
&= (x +5)(x^2 -5x +25)
\end{align*}
