Help me solve this please:
lim [(x+1)^2 - 1] / x
x-> 0
I got 0. I don't think that's right though.
There are many more ways than three to solve limits. The easiest way is to find some way to simplify the function so that you can factor and cancel any terms that will end up making an indeterminate form, which like you said, might involve factoring or conjugation.
Substitution is only used if the function is continuous at the point you are approaching, or once you have done enough to be able to substitute without resulting in an indeterminate form.