Đáp án:
Giải thích các bước giải:
`3, 4y^2 + 4y + 1`
`= (2y)^2 + 2.2y.1 + 1^2`
`= (2y + 1)^2`
`6, (x - y)^3 - (x + y)^3`
`= [(x - y) - (x + y)][(x - y)^2 + (x - y)(x + y) + (x + y)^2]`
`= (x - y - x - y)(x^2 - 2xy + y^2 + x^2 - y^2 + x^2 + 2xy + y^2)`
`= -2y(3x^2 + y^2)`
`9, 81x^2 - 64y^2`
`= (9x)^2 - (8y)^2`
`= (9x - 8y)(9x + 8y)`
`10, 8x^3 - 1/8`
`= (2x)^3 - (1/2)^3`
`= (2x - 1/2)[(2x)^2 + 2x. 1/2 + (1/2)^2]`
`= (2x - 1/2)(4x^2 + x + 1/4)`
