$15=\frac{k}{15}$

$\lim_{x\to-3}\left(\frac{x^2-8x-33}{x+3}\right)$

$sin\left(x\right)cos\left(x\right)=\frac{cos\left(x\right)-cos^3\left(x\right)}{sinc\left(x\right)}$

$\lim_{x\to-1}\left(\frac{3x^4+9x^3+x+7}{x+1}\right)$

$\left(\frac{1}{2}x^2+\frac{3}{5}x^3\right)^2$

$-85+1-6$

$9xy^3\cdot2xy^3z$