I'm stuck on a particular maths question which asks;

Write $\displaystyle (1 + \sqrt{5})^3$ in the form $\displaystyle a + b\sqrt{5}$, where a and b are integers.

Idohave a worked solution to this problem, but it isn't much help, as I'm uncertain as to how to expand cubic brackets.

Could someone please explain how to expand backets of the form $\displaystyle (a + b)^3$ and $\displaystyle (a - b)^3$?