\(x^2+3x+x+3=\left(x+1\right)\left(x+3\right)\)

\(=x^2+x+3x+3=x\left(x+1\right)+3\left(x+1\right)=\left(x+1\right)\left(x+3\right)\)

\(x^2+x+3x+3=x\left(x+1\right)+3\left(x+1\right)=\left(x+1\right)\left(x+3\right)\)

\(x^2-4x-y^2+4=\left(x^2-4x+4\right)-y^2=\left(x-2\right)^2-y^2=\left(x-2-y\right)\left(x-2+y\right)\)

1. (x-3)²

2. (3y+2x)²

3. (1/5x-8y)(1/5x+8y)

4. (x-2y)(x²+2xy+4y²)

5. (4x-3-x-1)(4x-3+x+1)

(3x-4)(5x-2)

\(x^2-7x-8\\=x^2+x-8x-8\\=x(x+1)-8(x+1)\\=(x+1)(x-8)\)

(x²+6x+9) - y²= (x+3)²-y²= (x+3-y) (x+3+y)

(x²+6x+9) - y²

= (x+3)²-y²

= (x+3-y) (x+3+y)

(x2+6x+9) - y2= (x+3)2-y2
= (x+3-y) (x+3+y)

=(x-2y)(x+2y)-2(x-2y)

=(x-2y)(x+2y-2)

\(x^2-4y^2-2x+4y=\left(x-2y\right)\left(x+2y\right)-2\left(x-2y\right)=\left(x-2y\right)\left(x+2y-2\right)\)

x^2-2x+1-4y^2+4y-1

=(x-1)^2-(2y-1)^2

=(x-1-2y+1)(x-1+2y-1)

=(x-2y)(x+2y)

\(x^2-11x+3\\ =\left(x^2-4x+4\right)-7x-1\\ =\left(x-2\right)^2-\left(\sqrt{7x+1}\right)^2\\ =\left(x-2-\sqrt{7x+1}\right)\left(x-2+\sqrt{7x+1}\right)\)

PHU HUYNH

\(=x^2+x-6x+6\\ =x\left(x+1\right)-6\left(x+1\right)\\ =\left(x+1\right)\left(x+6\right)\)

\(x^2-3x-4=x^2+x-4x-4=x\left(x+1\right)-4\left(x+1\right)=\left(x-4\right)\left(x+1\right)\)

`x^2 - 3x - 4`

`<=> x(x - 3)-4`