$\lim_{x\to0}\left(\frac{\sqrt{x^2+1}-1}{\sqrt{x^2+9}-3}\right)$

$\cos\left(50\right)-\cos\:\left(50\right)$

$\left(y+3\right)\left(-y+9\right)$

$-6n+9$

$\int19x^3\cdot e^xdp$

$\left(e^x\cdot\:\:y+1\right)dx+\left(e^x-1\right)dy=0$

$\int x^3\cdot\cos\left(6x\right)dx$