Hello, simple limit question that has been on my mind. Is there a simple rule of thumb when not to simplify an equation?

Here is the problem that I have been working on:

lim as x ->2 of

(x^2+4x-12)/(x^2-2x)

If I simplify the above I get 1+(6/x), but (this is a big but) I totally miss the fact that in the original equation x != 2. Looking at it now, its fairly obvious that I did this wrong. My concern is that for a more complex problem the fact that x != some number might not be that apparent.

Is there any little tricks that I could use in other problems to know when not to simplify?

Thanks.