$$7\left(a+b\right)$$

$$\left(4x^2-1\right)^2$$

$$\left(\frac{3}{n}\right)\left(\frac{9\left(a^2+1\right)}{n^2}+\frac{6\left(a-1\right)}{n}+1\right)$$

$$2x^5-2x^4-34x^3-30x^2$$

$$\frac{d}{dx}+20y=24$$

$$\frac{dy}{dx}=\frac{2x^3+2-x}{2x^2}$$

$$\lim_{x\to0}\left(\frac{\left(1-\cos\left(3x\right)\left(x^2+16\right)\right)}{x}\right)$$