$$\lim_{x\to\infty}\left(15+4x\right)$$

$$\left(3cd-9\right)\left(3cd+9\right)$$

$$\sqrt[3]{81x^2y^4}$$

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

$$x\frac{dy}{dx}+4y=x^2-x$$

$$\left(3ye^{4x}\right)\frac{dy}{dx}=\frac{2x}{3y^2}$$

$$\frac{x^3-6x^2+3x+10}{x+1}$$