TOÁN 8

$$\left(A+B\right)^2=A^2+AB+B^2$$

$$\left(A-B\right)^2=A^2-2AB+B^2$$

$$x^2+2xy+y^2=x^2+y^2$$

$$x^2-2xy+y^2=x^2-y^2$$

$$C^2+2CD+D^2=\left(C-D\right)^2$$

$$x^2+y^2=\left(x+y\right)^2+2xy$$

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

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

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

$$A^2+2AB-B^2$$  

$$A^2+2AB+B^2$$  

$$A^2-2AB+B^2$$  

$$A^2-2AB-B^2$$  

$$x^2+9$$  

$$x^2+6x+9$$  

$$4x^2-4x+1$$  

$$4x^2+4x-1$$  

$$9-6x+4x^2$$  

$$9+12x+4x^2$$  

$$4x^2-12x+9$$  

$$9-12x+x^2$$  

$$2x^2+x+\frac{1}{2}$$  

$$4x^2+4x+\frac{1}{2}$$  

$$4x^2+2x+\frac{1}{4}$$  

$$2x^2+x+\frac{1}{4}$$  

$$9+4x^2$$  

$$9-4x^2$$  

$$9-12x\ +4x^2$$  

$$9+12x+4x^2$$  

(x + 1)(x - 3)

(x + 3)(x + 1)

(x - 1)(x - 3)

(x + 3)(x - 1)

$$2x^3-6x^2+8x$$

$$2x^3+6x^2-8x$$

$$2x^3+6x^2-8$$  

$$2x^3-6x^2+8x$$