$\frac { - t ^ { 3 } + 3 t ^ { 2 } - 9 t } { 4 }$

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

$\int\frac{\cot^2\left(t\right)}{\csc\left(t\right)}dt$

$\sqrt{2x+3}=\sqrt{x+1}$

$\int x^2\left(3x^3-6\right)^3dx$

$16z^2+40z+25$

$18x^2+12$