Expand the numerator.

Combine like terms to simplify the numerator.

Factor out an h.

Simplify the fraction by 'cancelling out' the h.

Evaluate the limit as h→0.

If your answers do not agree, you probably made an Algebraic error in part (a).

also sketch the f '(x) you found in part (a) and part (b).

The two graphs should be close, but not identical since part (c) uses a finite value for h.