lim x^2-9/x+3 = -6
x-->3

I think that you meant:


What happens if you factorise the denominator? :)

Please use proper grouping symbols. You are in calculus.

Are you sure there is not a typo.
x should perhaps approach -3 instead of 3?

Here's why I ask:

The numerator is a difference of two squares.





If x approached 3, the limit would be 0.