Đáp án:
`10, x^2 - 9y^2 = x^2 - (3y)^2`
`= (x - 3y)(x + 3y)`
`11, (2x + 1)^2 - 4`
`= (2x + 1)^2 - 2^2`
`= (2x + 1 +2)(2x + 1 - 2)`
`= (2x + 3)(2x - 1)`
`12, x^4 - 2x^2`
`=x^2 (x^2 - 2)`
`= x^2 [x^2 -` ($\sqrt{2}$)²`]`
`= x^2 (x -` $\sqrt{2}$)(`x +` $\sqrt{2}$)
`13, x^2 - 6x - y^2 + 9`
`= (x^2 - 6x + 9) - y^2`
`= (x^2 - 2.x.3 + 3^2) - y^2`
`= (x - 3)^2 - y^2`
`= (x - 3 -y)(x - 3 + y)`
`14, x^3 - 1 = x^3 - 1^3 = (x - 1)(x^2 + x + 1)`
`15, x^2 - 6x = x(x - 6)`
