$$\lim_{x\to\infty}\left(\frac{-2x^3+4x^5}{x^3+4x^5}\right)$$

$$\frac{2x-9}{10}$$

$$\left(x+1\right)^2\left(x-1\right)^2$$

$$\frac{x^5+243}{x+6}$$

$$\frac{\cos^2\left(x\right)}{\sin\left(x\right)}=\frac{\cot\left(x\right)}{\sec\left(x\right)}$$

$$-7x=0$$

$$-\frac{42}{0}$$