$$\sin\left(x\right)\left(9\cos\left(x\right)-1\right)$$

$$\lim_{x\to0}\left(\frac{sinx}{38.4x}\right)^{\frac{1}{x}}$$

$$-4x+1<2x$$

$$\left(5x^2y^5\right)\left(2x^5y^{-8}\right)$$

$$x+12=17$$

$$x^2+9<0$$