$\lim_{x\to1}\left(\frac{ln\:x}{13x-x^2-12}\right)$

$\left(x+\frac{3}{8}\right)^2$

$2m-4n-7n$

$-3y^3-3y^3$

$\left(4a-7y\right)\left(4a+7y\right)$

$\lim_{x\to\frac{\pi}{2}}\left(\frac{tan^2x}{sec^2x}\right)$

$\lim_{x\to0}\left(\frac{\cos^2\left(x\right)-4\cos\left(x\right)+3}{x\sin^3\left(x\right)}\right)$