$$\left(a+\frac{2}{\:3}\right)\left(a-\frac{5}{6}\right)$$

$$\frac{dy}{dx}=1.2y\left(x-y\right)$$

$$\left(x.y\right)=x\left(y+4\right)+y+4$$

$$-81x^4+9$$

$$\left(x^2-y\right)y'+2x^3+2xy$$

$$18+2.\left(5-9\right)-3.\left(9-7\right)$$

$$-8x^2+6x-11=0$$