Question

I'm trying to find out how to do this limit. The answer is 6, but I don't know how to get it.

http://www.wolframalpha.com/input/?i=lim+%28x%2Cy%29+approaches+%289%2F2%2C9%2F2%29+of+%28x%2By-9%29%2F%28%28x%2By%29%5E1%2F2-3%29

Answer 1

Note that:\[x+y-9=(\sqrt{x+y}-3)(\sqrt{x+y}+3)\](Difference of two squares)

Answer 2

Nifty, thanks, I thought it looked similar, I shoulda suspected something like that!