$\left(\frac{3a^{-2}}{4b^{-\frac{1}{3}}}\right)^{-1}$

$12\cdot13\cdot4$

$\left(6m+11\right)^2$

$\left(x+8y\right)\left(x-7y\right)$

$\frac{1\:+\:\tan\left(a\right)}{1+\:\cot\left(a\right)}=\tan\left(a\right)$

$x\cos\frac{1}{2}x^2$

$\frac{\left(4mn-8m^2n-2mn\right)}{\left(2mn\right)}$