Đáp án+Giải thích các bước giải:

a) `(2x + 5y)^3`

`= (2x)^3 + 3 * (2x)^2 * 5y + 3 * 2x * (5y)^2 + (5y)^3`

`= 8x^3 + 60x^2y + 150xy^2 + 125y^3`

`-------`

 `(2x - 5y)^3`

`= (2x)^3 - 3 * (2x)^2 * 5y + 3 * 2x * (5y)^2 - (5y)^3`

`= 8x^3 - 60x^2y + 150xy^2 - 125y^3`

`-------`

`8x^3 + y^3`

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

`= (2x + y)[(2x)^2 - 2x * y + y^2]`

`= (2x + y)(4x^2 - 2xy + y^2)`

`-------`

`8x^3 - y^3`

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

`= (2x - y)[(2x)^2 + 2x * y + y^2]`

`= (2x - y)(4x^2 + 2xy + y^2)`

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b) `(x + 5)^3`

`= x^3 + 3 * x^2 * 5 + 3 * x * 5^2 + 5^3`

`= x^3 + 15x^2 + 75x + 125`

`-------`

`(2x - 5)^3`

`= (2x)^3 - 3 * (2x)^2 * 5 + 3 * 2x * 5^2 - 5^3`

`= 8x^3 - 60x^2 + 150x - 125`

`-------`

`1 + y^3`

`= 1^3 + y^3`

`= (1 + y)(1 - y + y^2)`

`-------`

`1 - y^3`

`= 1^3 - y^3`

`= (1 - y)(1 + y + y^2)`

`\ttcolor{red}{#T2}`