$3a+18-12a+15a$

$64a^2+128ab+64b^2$

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

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

$\int\frac{1}{\left(x^2\sqrt{a^2-x^2}\right)}dx$

$\lim_{x\to0}\left(\frac{sin\left(x^3\right)}{sin^3\left(x\right)}\right)$

$\int sec^4\left(5t\right)dt$