$$\left(5x+2y+4\right)^2$$

$$\left(4x^6-10y^5-5y^4\right)\left(-2x^3\right)$$

$$6a+6b$$

$$cot^2xsec^2x=cot^2x+1$$

$$\lim_{x\to0}\left(\frac{\sqrt{\left(x+a\right)}-\sqrt{a}}{x}\right)$$

$$4x^4-25x^2$$

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