How to simplify this rational expression?

This expression should be extremely easy to simplify, but for some reason I can't do it.

$$\frac{x^4-1}{x-1}$$

I know it simplifies down to this, but I don't know how to get there

$$x^3+x^2+x+1$$

This is a very basic question on my calculus worksheet, I would appreciate if anyone could explain how the first expression simplifies down to the second.

Answer

Write it as the difference of two squares $$\frac{(x^2-1)(x^2+1)}{(x-1)}$$
$$\frac{(x+1)(x-1)(x^2+1)}{(x-1)}$$
$$(x+1)(x^2+1)=x^3+x^2+x+1$$