$6a+7b-5a+8b$

$\lim_{x\to\infty}\left(\frac{-x}{x^2+1}\right)$

$\left(e^{2x}+4\right)\frac{dy}{dx}=y$

$\left(28\::\:7\:+1\:-4\right)x\:10\:+\left(5\:x\:8-40\::2\right)-15\:$

$a\left(n-2\right)+\left(n-2\right)$

$\frac{dy}{dx}\left(y=\sqrt{x}\left(3x-1\right)\right)$

$\frac{\left(sec\left(x\right)\right)\left(sec\left(x\right)-1\right)}{sin^2x}$