$\left(2x+3\right).\left(2x-5\right)-\left(x-3\right)^2$

$\frac{2}{1+cosx}-tan^2\left(\frac{x}{2}\right)=1$

$\frac{5x^2-x-160}{x^2-25}$

$\frac{4x+5}{6x^2-x-12}-\frac{5x}{6x^2-x-12}\:$

$\left(t^2-12t+11\right)\frac{dy}{dt}=y$

$\lim_{x\to2}\left(3-x\right)^{\cot\left(\pi x\right)}$

$\int 10 \times \sqrt { 1111 - x ^ { 2 } } d x$