Đáp án +Giải thích các bước giải:
`a)(x+2y)^2`
`=x^2 +2.x.2y + (2y)^2`
`=x^2 +4xy +4y^2`
`b)(7-x)^2`
`=7^2 -2.7.x +x^2`
`=49 -14x +x^2`
`c) (x-7)^2`
`=x^2 -2.x.7 +7^2`
`=x^2 -14x +49`
`d) (3x- 1/2)^3`
`=(3x)^2 - 3.(3x)^2 .1/2 + 3.3x. (1/2)^2 -(1/2)^3`
`=27x^3 - 3.9x^2 .1/2 + 3.3x. 1/4 - 1/8`
`=27x^3 - 27/2 x^2 + 9/4 x -1/8`
`e) (1/2 -3x)^3`
`=(1/2)^3 - 3. (1/2)^2 .3x +3. 1/2 .(3x)^2 - (3x)^3`
`= 1/8 - 3. 1/4 .3x + 3. 1/2 . 9x^2 -27x^3`
`=1/8 - 9/4 x + 27/2 x^2 -27x^3`
