see the first post here.

good. now multiply by the conjugate of the numerator over itself. this is a standard trick. (note that the top becomes the factorized for of the difference of two squares).

lim = ( f(a+h)-f(a) ) / (h)

h->0

= f(1+h)-f(1) / h

= (2 sqrt(1+h) - 2) / h

This is where I have gotten to. substituting in now will give me a 0 in my denominator. So where would I go next?

so you have

now simplify and continue