Hello, thaliaj_df!

This is a messy problem . . .

They could have easily made two problems out of it.

I must assume that you know the four steps of the First Principles:From first principles, find the derivative of: .

. . (1) Find . . . Replace with ... and simplify.

. . (2) Subtract . . . Subtract the original function ... and simplify.

. . (3) Divide by . . . Factor and reduce.

. . (4) Take the limit as . . . Let and see "what's left."

We will differentiate the two fractions separately . . .

Let

. . . . . . . . . . . .

. . . . . . . . . . . .

. . . . . . . . . . . .

. . . . . . . . . . . . . . .

Hence: .

Let

Hence: .

Therefore: .