$$\lim_{x\to5}\left(\frac{2x-10}{x-5}\right)$$

$$\left(u+10\right)\left(u-10\right)$$

$$x^2+7x=98$$

$$\frac{3x^2-5x+2}{x-5}$$

$$5\left(-2n-3\right)+2n$$

$$\int\frac{5x^3+2x^2-40x-21}{x^2-9}dx$$

$$\lim_{x\to\infty}\left(5x^3+8x\right)$$