$\lim_{x\to\infty}\left(\frac{\sin\left(\frac{2}{x}\right)}{\sin\left(\frac{1}{x}\right)}\right)$

$9^0-4$

$14x^4+21x^3+9x^2$

$\left(-1\right)^n\left(\frac{\left(x-3\right)^n}{2n+1}\right)$

$3+\left(5-4\right)-\left(6-7\right)$

$81x^2-6x+3$

$5000\cdot\frac{2}{100}\cdot10$