Đáp án:
a, `(x + 2y)^2 = x^2 + 2 . x . 2y + (2y)^2`
` =x^2 + 4xy +4y²`
b, `(3x - 2y)^2 = (3x)² - 2 . 3x . 2y + (2y)^2`
` =9x^2 - 12xy +4y²`
c, `(2x - 1/2)^2 = (2x)^2 - 2 . 2x . 1/2 + (1/2)^2`
` = 4x² - 2x + 1/4`
d, `(x/2 - y)(x/2 + y) = (x/2)^2 - y^2`
`=(x²)/4 - y^2`
e, `(x+1/3)^3 = x³ +3 x² . 1/3 + 3x . (1/3)^2 + (1/3)³`
`= x³ + x² + 1/3x + 1/27`
f,`(x - 2)(x² + 2x + 4)`
`=(x - 2)(x² + 2x + 2²)`
`=(x - 2)³`