$2x+2$2x+2

$\displaystyle \frac{2x}{x-1}$\displaystyle \frac{2x}{x-1}

$\displaystyle \frac{2x}{x^2-1}$\displaystyle \frac{2x}{x^2-1}

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