Primitive of Power

Theorem
Let $n \in \R: n \ne -1$.

Then:
 * $\displaystyle \int x^n \ \mathrm d x = \frac {x^{n+1}} {n+1} + C$

where $C$ is an arbitrary constant.

That is:
 * $\dfrac {x^{n+1}} {n+1}$ is a primitive of $x^n$.

Proof
When $n = -1$ we have $n + 1 = 0$, and $\dfrac {x^{n+1}} {n+1} = \dfrac {x^0} 0$ is undefined.