$\int_{3\pi}^{\infty}\left(\cos\left(x\right)\right)dx$

$\frac{4x^5+6}{2x^3+2}$

$\frac { 15 x ^ { 5 } + 21 x ^ { 2 } + 6 } { 3 x + 3 }$

$3\left(2x^3-5x^2+x-1\right)$

$\left(x-21\right)\left(x+21\right)$

$18+12:\left(-\left(-8\right)+3x\left(-2\right)\right)$

$\frac{dy}{dx}-2y=2$