$\lim_{x\to0}\left(e^x+7x\right)^{\frac{9}{x}}$

$\frac{dy}{dx}=\frac{xy-y}{y+1}$

$\lim_{x\to-\infty\:}\left(\frac{x^2-43}{x-8}\right)$

$\left(2xy-5y^2\right)^2$

$-18m^2-17mn+15n^2+20^2+3mn-17n^2+5m^2+18mn+7n^2$

$\frac{dy}{dx}=\frac{xsecy}{ye^{t^2}}$

$\left|7\right|.9.\left|0\right|$