$$\lim_{x\to0}\left(\frac{7^x-2^x}{x}\right)$$

$$x^2+12x-289$$

$$\frac{\csc x+\cot x}{\tan x+\sin x}$$

$$y=x-y$$

$$\left(3x+7\right)\left(9x^2-21x+49\right)$$

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

$$\frac{d}{dx}\left(\frac{400x}{\ln\left(2x+7\right)}\right)$$