$f\left(x\right)=x^2-\frac{4}{x}$

$-\left(5x+2y\right)^3$

$-3^3-6\left(-2\right)-2$

$\lim_{x\to0}\left(\frac{7cosx-7}{2x}\right)$

$\left(3x+5\right)\left(x-18\right)-9\left(x-5\right)^2$

$\frac{24x^3+16x^2-8x}{-4x}$

$\lim_{x\to\infty}\left(\frac{5\cos\left(x\right)+9\sin\left(3x\right)-5}{\sin\left(4x\right)-\sin\left(5x\right)+2x}\right)$