$\lim_{x\to\infty}\left(\frac{x^2-2x^5}{3+7x^4}\right)$

$f\left(x\right)=\frac{4xb}{2a-6x}$

$\left(-7x^2+a^2\right)\left(7x^2-b\right)$

$\frac{2}{5}xy^2.\:\frac{7}{10}x^3y$

$\frac{dy}{dx}+\left(\frac{1}{2\sqrt{x}}\right)y=\left(\frac{1}{2\sqrt{x}}\right)$

$\int x^2e^{15x}dx$

$\lim_{x\to0}\left(\frac{e^2-1}{3+x^2}\right)$