$3a-5+3a-7$

$\frac{dy}{dx}=\frac{xy-2x-y+2}{xy-3x+3y-9}$

$13x^2y^2+65x^3y$

$\frac{cos\left(a\right)}{1+sin\left(a\right)}-\frac{\cos\left(a\right)}{1-\sin\left(a\right)}=-2\tan\left(a\right)$

$\left(2s^2+5\right)-5\left(3s^2+8\right)$

$u^2-5u+2$

$\frac{d}{dx}\frac{tan^2x}{2}$