$\lim_{x\to\infty}\sqrt{x^2+9x}-\sqrt{x^2+5x}$

$\frac{5x^2y^4-10x^3y^2-15x^4y}{-5xy}$

$\left(3xy^2\:+\:5x^3y^3\right)\left(3xy^2\:-\:5x^3y^3\right)$

$\lim_{x\to infinity}\left(\frac{e^x}{e^{2x}}\right)$

$\lim_{x\to\infty}\left(x+e^x\right)^{x^{-1}}$

$\frac{d^{-2}.d^5}{d^{-7}}$

$\frac{2x^5-10x^3-2x^2+10}{x^2+5}$