$$\lim_{x\to\infty}\left(\frac{6x^2}{e^{5x}}\right)$$

$$\int\frac{x}{\left(x^2-7\right)^2}dx$$

$$\frac{\frac{x^2+2x-8}{x^2-3x-4}}{\frac{x^2-4x+1}{x^2-6+8}}$$

$$\int\left(2-x\right)\cdot\cos\left(px\right)dx$$

$$\left(z^2+9\right)\left(z-3\right)\left(z+3\right)+81$$

$$\lim_{x\to\infty}\left(\frac{ln\left(7x+2\right)}{ln\left(3x+7\right)}\right)$$

$$x^2-4x-21=0$$