$\lim_{x\to\infty}\left(\frac{\pi-2\arctan\left(x\right)}{e^{\frac{3}{x}-1}}\cdot e^{-x}\right)$

$\lim_{x\to-1}\left(6.28\right)$

$\left(x+3\right)\left(x-3\right)+\left(4+x\right)\left(4-x\right)$

$\int\frac{4x-1}{\left(2x-1\right)\left(x+4\right)}dx$

$2x+3\le19$

$x^2x+9$

$9ax^3y^4=15x^2y^5$