$11-32$ Evaluate the limit$,$ if it exists.

$15.\underset{x5}{lim}\frac{x^2-6x5}{x-5}$

$12.\underset{x-3}{lim}\frac{x^{2}3x}{x^2-x-12}$

$13.\underset{x5}{lim}\frac{x^2-5x6}{x-5}$

$14.\underset{x4}{lim}\frac{x^{2}3x}{x^2-x-12}$

$15.\underset{t-3}{lim}\frac{t^2-9}{2t^{2}7t3}$

$16.\underset{x-1}{lim}\frac{2x^{2}3x1}{x^2-2x-3}$

$17.\underset{h0}{lim}\frac{(-5h{)}^2-25}{h}$

$18.\underset{h0}{lim}\frac{(2h{)}^3-8}{h}$

$19.\underset{x-2}{lim}\frac{x2}{x^{3}8}$

$20.\underset{t1}{lim}\frac{t^4-1}{t^3-1}$

$21.\underset{h0}{lim}\frac{\sqrt[\phantom{2}]{9h}-3}{h}$

$22.\underset{u2}{lim}\frac{\sqrt[\phantom{2}]{4u1}-3}{u-2}$

$23.\underset{x3}{lim}\frac{\frac{1}{x}-\frac{1}{3}}{x-3}$

$24.\underset{h0}{lim}\frac{(3h{)}^{-1}-3^{-1}}{h}$

$25.\underset{t0}{lim}\frac{\sqrt[\phantom{2}]{1t}-\sqrt[\phantom{2}]{1-t}}{t}$

$26.\underset{t0}{lim}(\frac{1}{t}-\frac{1}{t^{2}t})$

$27.\underset{x16}{lim}\frac{4-\sqrt[\phantom{2}]{x}}{16x-x^2}$

$28.\underset{x2}{lim}\frac{x^2-4x4}{x^4-3x^2-4}$

$29.\underset{t0}{lim}(\frac{1}{t\sqrt[\phantom{2}]{1t}}-\frac{1}{t})$

$30.\underset{x-4}{lim}\frac{\sqrt[\phantom{2}]{x^{2}9}-5}{x4}$

$31.\underset{h0}{lim}\frac{(xh{)}^3-x^3}{h}$

$32.\underset{h0}{lim}\frac{\frac{1}{(xh{)}^2}-\frac{1}{x^2}}{h}$