Hi Meagan,

Let me try a slightly different problem

Using the limit definition find the derivative of f(x) = 4/(5x³).

The limit definition of the derivative is

With my function the numerator of the limit fraction is

Factor the numerator of this expression as a difference of cubes and simplify. You will find a factor of -h. Now divide by h to obtain

.

Simplify. There is no longer an h in the denominator and you can see the result of taking the limit as h approaches zero.

I hope this helps,
Harley