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

$121x^4-4y^2$

$\lim_{x\to\infty}\left(\frac{e^{2x-5}}{3x}\right)$

$5y+4\left(3-2y\right)+6-y$

$\lim_{x\to6}\left(\frac{x^2-36}{x^2-6}\right)$

$12\left(x+1\right)^2-17\left(x+1\right)+6$

$4^3+5\cdot4-1$