$\frac{a-x}{\left(a+x\right)\left(a-x\right)^2}$

$\frac{d}{dx}\left(x+7\right)^3\left(7x-2\right)^5$

$\frac{1-\text{tg}^2a}{1+\text{tg}^2a}=1-2\text{sen}^2a$

$-9+2x+13+7x-10-12x$

$\csc\left(2x\right)=\:\frac{\sec\left(x\right)}{2\sin\left(x\right)}$

$4a^2-12a+16$

$\frac{\tan\left(x\right)^2-\sin\left(x\right)^2}{\cot\left(x\right)^2-\cos\left(x\right)^2}$