$\lim_{x\to0}\left(\frac{2^{-x}}{x^2}\right)$

$15xy-3x+4xy$

$\int\frac{\left(x^5-6x^3-6x^2-8\right)}{x^3+6x}dx$

$\left(4m-n\right)^2\:=\:16m^{2\:}-8\cdot m\cdot n+n^2$

$\left(\frac{3}{4}x^3+\frac{5}{3}x^2+\frac{6}{5}-\frac{1}{2}x^2\right)+\left(\frac{3}{2}x^3+\frac{8}{3}x^5+\frac{5}{3}-3x^3\right)$

$2\cdot10x-14$

$( a ) ( 3 a - x ^ { 2 } )$