`a)` `(HĐT : a^3-3a^2b+3ab^2-b^3)`
`(3-y)^3`
`=3^3-3.3^2.y+3.3.y^2-y^3`
`=27-27y+9y^2-y^3`
`b)` `(HĐT : a^3+3a^2b+3ab^2+b^3)`
`(3x+2y^2)^3`
`=(3x)^3+3.(3x)^2. 2y^2+3.3x.(2y^2)^2+(2y^2)^3`
`=27x^3+54x^2y^2+36xy^4+8y^6`
`c)` `(HĐT : a^3+3a^2b+3ab^2+b^3)`
`(x-3y^2)^3`
`=x^3-3.x^2. 3y^2+3.x.(3y^2)^2-(3y^2)^3`
`=x^3-9x^2y^2+27xy^4-27y^6`
`d)` `(HĐT : a^3-3a^2b+3ab^2-b^3)`
`(x/2-y)^3`
`=(x/2)^3-3.(x/2)^2.y+3.x/2.y^2+y^3`
`=x^3/8-(3x^2y^2)/4+(3xy^2)/2-y^3`
`e)` `(HĐT : a^3+3a^2b+3ab^2+b^3)`
`(x/2+ 4/3)^3`
`=(x/2)^3+3.(x/2)^2 . 4/3+3.x/2.(4/3)^2+(4/3)^3`
`=x^3/8+(12x^2)/12+(48x^2)/18+64/27`
`f)` `(HĐT : a^3-3a^2b+3ab^2-b^3)`
`((2x)/3-2y)^3`
`=((2x)/3)^3-3.((2x)/3)^2. 2y+3.(2x)/3.(2y)^2-(2y)^3`
`=(8x^3)/27-(24x^2y)/9+(24xy^2)/3-8y^3`
`=(8x^3)/27-(8x^2y)/3+8xy^2-8y^3`
`e)` `(HĐT : a^3-3a^2b+3ab^2-b^3)` và `(HĐT : a^3+3a^2b+3ab^2+b^3)`
`(x+y)^3+(x-y)^3`
`=x^3+3.x^2.y+3.x.y^2+y^3+x^3-3.x^2.y+3.x.y^2-y^3`
`=x^3+3x^2y+3xy^2+y^3+x^3-3x^2y+3xy^2-y^3`
`=x^3+x^3+3x^2y-3x^2y+3xy^2+3xy^2+y^3-y^3`
`=2x^3+6xy^2`
