Đáp án`+`Giải thích các bước giải:

 `6, (x - 1/3)^2`

`= x^2 - 2.x.1/3 + (1/3)^2`

`= x^2 - 2/3x + 1/9`

`7, (2/3x - 1)^2`

`= (2/3x)^2 - 2.2/3x . 1 + 1^2`

`= 4/9x^2 - 4/3x + 1`

`8, (3x-  5y)^2`

`= (3x)^2 - 2.3x. 5y + (5y)^2`

`= 9x^2 - 30xy + 25y^2`

`9, y^2 - 49`

`= y^2 - 7^2`

`= (y - 7)(y + 7)`

`10, 4x^2 -9`

`= (2x)^2 -3^2`

`= (2x - 3)(2x + 3)`

`***`sharksosad