The existence of a limit.
Theorem: If f is a function and c and L are real numbers, then the limit of f(x) as x approaches c is L if and only if:
\(\displaystyle \lim_{x\to c^{-}}f(x) \ = \ L \ and \ \lim_{x\to c^{+}}f(x) \ = \ L.\)
Now, in your above thread, is L a real number?, no because infinity is not a real number, hence the limit doesn't exist for either function..
\(\displaystyle \lim_{x\to2^{-}}\frac{1}{x-2} \ = \ -\infty, \ and \ \lim_{x\to2^{+}}\frac{1}{x-2} \ = \ \infty.\)
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\(\displaystyle \lim_{x\to2^{-}}\frac{1}{(x-2)^{2}} \ = \ \infty \ and \ \lim_{x\to2^{+}}\frac{1}{(x-2)^{2}} \ = \ \infty.\)
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