Đáp án+Giải thích các bước giải:
`(a+b+c)^3=[a+(b+c)]^3`
`(a+b+c)^3=a^3+(b+c)^3+3a(b+c)(a+b+c)`
`(a+b+c)^3=a^3+b^3+3b^2c+3bc^2+c^3+3a(b+c)(a+b+c)`
`(a+b+c)^3=a^3+b^3+c^3+3bc(b+c)+3a(b+c)(a+b+c)`
`(a+b+c)^3=a^3+b^3+c^3+(b+c)(3bc+3a^2+3ab+3ac)`
`(a+b+c)^3=a^3+b^3+c^3+3(b+c)(a^2+ac+ab+bc)`
`(a+b+c)^3=a^3+b^3+c^3+3(b+c)[a(a+c)+b(a+c)]`
`(a+b+c)^3=a^3+b^3+c^3+3(a+b)(b+c)(a+c)`