$5x-y+7-4x+13y+-1$

$\sin^2a+2\cos2a=2\cos a$

$-2^5\cdot15$

$\frac{dy}{dx}=\frac{-\left(x-xy^2\right)}{\left(y-yx^2\right)}$

$\lim_{x\to0}\left(\left(cosx\right)^{\frac{\pi}{2}-x}\right)$

$\lim_{x\to-\infty}\left(\frac{\left(2e^x-2\right)}{\sin\left(2x\right)}\right)$

$9mn+12m-2mn$