$\left(\frac{9^{-2}}{2^{-1}+3^{-1}+6^{-1}}\right)^{-1}$

$\lim_{x\to\infty}\left(\frac{\left(x+1\right)^{\frac{3}{2}}}{\left(x+2\right)^{\frac{3}{2}}}\right)$

$( 2 x ^ { 3 } + 5 y ) ^ { 2 }$

$ay'-y=1$

$x^2-8x+20$

$\lim_{x\to\infty}\left(sqrt\left(x^2+6x\right)-x\right)$

$2x-1>3x$