$\frac{dy}{dx}=\frac{1}{\left(y-x\right)}$

$\lim_{x\to\infty}\left(\frac{\left(6+10x^2\right)^{\frac{1}{2}}}{4+5x}\right)$

$\left(x^{a-1}+y^{b-2}\right)^2$

$-2\:\left(4x\:-\:5y\:-\:5x\right)$

$\frac{tan^2x}{\left(secx+1\right)^2}=\frac{secx-1}{secx+1}$

$x-3<2x$

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