$\lim_{x\to0}\left(\frac{\cos\left(3x\right)-\cos^2\left(3x\right)}{x\cdot\cos\left(3x\right)}\right)$

$\left(-11b+10\right)\left(-11b-10\right)$

$\frac{dy}{dx}=kx$

$\frac{d}{dx}y\tan x^2+\ln xy=2x^2+3y^3$

$\sin\left(\frac{\pi}{8}\right)\cos\left(\frac{\pi}{8}\right)$

$9x^2+30+25\left(3x+5\right)^2$

$\left(3x^2+45\right)^2$