Answer
$ (x - 3)(x^2 +3x +9)$
Work Step by Step
Since $x^3-27$ is a difference of the two cubes $x^3$ and $3^3$, then by making use of the difference of two cubes
$$a^3 - b^3 = (a - b)(a^2 +ab + b^2),$$
we have
\begin{align*}
x^3 - 27&=x^3-3^3\\
&= (x - 3)(x^2 +3x + 3^2)\\
&= (x - 3)(x^2 +3x +9)\end{align*}
