$$\left(2a+3b\right)\left(2a-3b\right)=4a^2-9b^2$$

$$\int\left(1-\cos2\left(3x\right)\right)dx$$

$$x^2-2,2x$$

$$n^{2}y+20n^{2}y-49n^{2}y$$

$$\sqrt{5}+2\cdot\sqrt{5}-\left(5\cdot\sqrt{5}\right):5$$

$$\frac{d}{dx}x^2+2xy-y^2+x=46$$

$$2x+5x-x+6x-9x$$