Consider the function $f(x) = 2x^{3}-4x$ on the interval $[ -2 , 2 ]$.

Find the average or mean slope of the function on this interval.

By the Mean Value Theorem, we know there exists at least one $c$ in the open interval $( -2 , 2 )$ such that $f'( c)$ is equal to this mean slope.
For this problem, there are two values of $c$ that work: