Determine the following limits using methods learned in class.

a$.\underset{x1}{lim}\frac{x-4}{(x3)}$

b$.\underset{x{9}^{-}}{lim}\frac{x-6}{x(5-x)}$

c$.\underset{x}{lim}\frac{2-x}{x3},[$This tro$-$sided limit requires finding some one$-$sided limits forse$]$