$( 3 + y ^ { 2 } ) \cdot ( 3 x - y ^ { 2 } )$

$z\left(x+1\right)^2$

$\frac{dy}{dx}=2x+\frac{y}{x-1}$

$10d^2y^2-20d^2y$

$\frac{x}{4x^2+2x}$

$\frac{3x+1}{4}-\frac{1}{3}\le\frac{2}{15}\left(3x+2\right)+\frac{4\left(1-x\right)}{3}$

$\lim_{x\to\infty}\left(\frac{x^6}{2^x}\right)$