$\lim_{x\to0}\left(\frac{\sqrt{a+2x}-\sqrt{a-4x}}{x}\right)$

$\int ctg^2csec^3\left(x\right)dx$

$\int x^{\frac{2}{3}}\left(12x^{-\frac{1}{2}}-11x^{-\frac{2}{3}}+11-12x^{-\frac{1}{3}}\right)dx$

$-\left(a-6b\right)\left(a+6b\right)$

$2\left(\frac{2}{y}\right)\left(\frac{1}{2}\right)$

$-6a+19-5a$

$30x^7x^{10}$