mọi người giúp mình với ạ

Đáp án:

Câu `1.`

`a,` `(4x + 7)^2`

`= (4x)^2 + 2.4x . 7 + 7^2`

`= 16x^2 + 58x + 49`

~~~~~~~~~~~~~~~

`b,` `(6x - 1/3y)^2`

`= (6x)^2 - 2. 6x . 1/3y + (1/3y)^2`

`= 36x^2 - 4xy + 1/9y^2`

~~~~~~~~~~~~~~~

`c,` `(3x^2 - 5xy^3).(3x^2 + 5xy^3)`

`= (3x^2)^2 - (5xy^3)^2`

`= 9x^4 - 25x^2y^6`

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Câu `2.`

`a,` `x^2 - 6xy + 9y^2`

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

`= (x - 3y)^2`

~~~~~~~~~~~~~~~

`b,` `4x^2 + 4x + 1`

`= (2x)^2 + 2. 2x . 1 + 1^2`

`= (2x + 1)^2`

`#dariana`