Đáp án:
Giải thích các bước giải:
Bài `1`
`8, 1/8 - 8x^3 = (1/2)^3 - (2x)^3 = (1/2 - 2x)[(1/2)^2 + 1/2 .2x + (2x)^2]`
`= (1/2 - 2x)(1/4 + x +4x^2)`
`9, 27x^3 - a^3 = (3x)^3 - a^3 = (3x - a)[(3x)^2 + 3x.a + a^2]`
`= (3x - a)(9x^2 + 3ax + a^2)`
`10, 1/27 + x^3 = (1/3)^3 + x^3 = (1/3 + x)[(1/3)^2 - 1/3 .x + x^2]`
`= (1/3 + x)(1/9 - 1/3 x + x^2)`
`11, x^3 + 125 = x^3 + 5^3 = (x + 5)(x^2 - 5x + 25)`
Bài `2`
`a, x^3 + 3x^2 + 3x + 1`
`= x^3 + 3.x^2 .1 + 3.x.1^2 + 1^3`
`= (x + 1)^3`
`b, 27y^3 - 9y^2 + y - 1/27`
`= (3y)^3 - 3.(3y)^2 . 1/3 + 3.y. 1/3 - (1/3)^2`
`= (3y - 1/3)^3`
