$\lim_{x\to0}\left(\frac{ln\left(1+x\right)-\sin\left(x\right)}{x\cdot\cos\left(x\right)}\right)$

$20+90+51e$

$\left(x^7+y^7\right)\left(x-7\right)$

$4\left(5x^3+1\right)^2$

$\left(5m^2-3n\right)\left(5m^2+3n\right)$

$\frac{dy}{dx}=x\ln\left(2x\right)$

$\lim_{x\to\infty}\left(\frac{x^2}{lnx}\right)$