$$x ^ { 4 } - a ^ { 4 }$$

$$\frac{x}{\frac{2}{w}}$$

$$7xy+5x+5xy$$

$$\lim_{x\to0.1}\frac{\sin\left(x\right)}{1+\tan\left(x\right)}$$

$$\cos\left(x\right)-09=0$$

$$\lim_{x\to\infty}\left(\frac{7x}{7x-2}\right)^{x-1}$$

$$7x^2+21x-2<\:0$$