$cos\left(x\right)sen\left(y\right)=\frac{1}{2}sen\left(x+y\right)-\frac{1}{2}sen\left(x-y\right)$

$-\left(-7-12\right)$

$4x^4-2x^2-6$

$\left(6x^2-y\right)dx+\left(19y^3-x\right)dy=0$

$\frac{dx}{dt}=3t^2\left(x^2+4\right)$

$-2\left(+x^3-3x^2-144x+440\right)$

$\left(3-\left(-8\right)\right)+\left(-2\right)$