$\lim_{x\to2}\left(\frac{x^2+4}{x^2-3x+2}\right)$

$\left(2-2\sin\left(x\right)\right)\left(1+\sin\left(x\right)\right)$

$\left(19a-b\right)\left(19\:a+b\right)$

$\left(xsenx-ycosx\right)^2+\left(xcosx+ysenx\right)^2$

$\left(\frac{x}{2}\right)^4\frac{\left(8x\right)^2}{x^{-1}x^{10}}$

$\int\frac{-15x^2}{\left(2-5x^3\right)^2}dx$

$\left(d+12\right)\left(d-15\right)$