$\int sin\left(9x\right)\cdot\cos\left(5x\right)dx$

$\lim_{x\to0}\left(\frac{x^2+49x}{7sen\left(x\right)}\right)$

$\frac{dy}{dx}-\frac{1}{x}y=1-\frac{1}{x}$

$\left(1+5xy^4\right)^2$

$\left(3a^5c^3\right)^4\left(2a^2c^2\right)^{-3}$

$\left(3y^2+x\right)^2$

$8x^5y-4x^3y^3+12x^2y^2$