$$\frac{2}{5}\cdot35$$

$$\frac{2\sin\left(x\right)\cos\left(x\right)}{1-\cos2x}$$

$$57,2+3,768$$

$$\frac{d}{dx}\left(-0.25x^3+100x\right)$$

$$-10x-6=-10x$$

$$\frac{dy}{dx}\:-\frac{y}{x}=\frac{x}{3y}$$