The Power Rule and other basic rules


The first four rules for taking derivatives are:

  1. $(c)'=0$, namely the derivative of a constant is 0.

  2. $(x^n)'=nx^{n-1}$, for any constant $n$ (a.k.a., the power rule).
    If $n$ is a non-negative integer, this makes sense for all values of $x$. If $n$ is a negative integer, this makes sense for all $x \ne 0$, and if $n$ is a (positive or negative) fraction, then this makes sense for $x>0$.

  3. $(cf(x))'=c\cdot f'(x)$, if $c$ is a constant.

  4. $\left(f(x)+g(x)\right)'=f'(x)+g'(x)$ and $\left(f(x)-g(x)\right)'=f'(x)-g'(x)$.

The following videos develop these rules.


The Derivative of a Constant


The Power Rule


The Constant Multiple Rule


The Sum and Difference Rules