$\left(3x^2-2xy\right)dx+\left(4y^3-x^2+3\right)dy=0$

$ln63=lnz+ln7$

$\lim_{x\to-\infty}\left(\frac{8e^x}{e^x-9}\right)$

$f\left(x\right)=\left(x^3+6x^2-2x+1\right)^{-3}$

$\lim_{x\to\frac{\pi}{2}}\left(1-\frac{sin\left(x\right)}{cos\left(x\right)}\right)$

$\frac{1+\sin\left(x\right)^2}{\cos\left(x\right)^2}=2\sec\left(x\right)-1$

$\ln\left(x\right)-\ln\left(14\right)=0$