$$1-a^6$$

$$\left(2x-6\right)\left(x-3\right)$$

$$3x^3y+2x^2y^2-6x^2y=x^2y$$

$$\frac{dy}{dx}=0,4-\frac{2y}{25}$$

$$\frac{1-cos\left(x\right)}{1+cos\left(x\right)}=cot^2\left(x\right)-2cot\left(x\right)csc\left(x\right)+csc^2\left(x\right)$$

$$\left(a+12\right)\left(a+20\right)$$

$$5\sqrt{63}-7\sqrt{28}-9\sqrt{36}$$