Answer
$x^{3}-8$
Work Step by Step
Distribute:
$(x-2)(x^{2}+2x+4)\\
=x(x^{2}+2x+4)-2(x^{2}+2x+4)$
$=x^{3}+2x^{2}+4x-2x^{2}-4x-8$
Combine like terms:
$=x^{3}-8$
ALTERNATIVELY:
We could have recognized the formula for the difference of cubes
$A^{3}-B^{3}=(A-B)(A^{2}+AB+B^{2})$ with $A=x \text{ and } B=2$