`(x+1)^3+(x-2)^3=(2x-1)^3`
`<=>x^3+3x^2+3x+1+x^3-6x^2+12x-8=8x^3-12x^2+6x-1`
`<=>2x^3-3x^2+15x-7=8x^3-12x^2+6x-1`
`<=>6x^3-9x^2-9x+6=0`
`<=>6x^3+6x^2-15x^2-15x+6x+6=0`
`<=>6x^2(x+1)-15x(x+1)+6(x+1)=0`
`<=>(x+1)(6x^2-15x+6)=0`
`<=>(x+1)(6x^2-12x-3x+6)=0`
`<=>(x+1)[6x(x-2)-3(x-2)]=0`
`<=>(x+1)(x-2)(6x-3)=0`
`<=>`\(\left[ \begin{array}{l}x+1=0\\x-2=0\\6x-3=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=-1\\x=2\\x=\dfrac12\end{array} \right.\)
Vậy `S={-1;1/2;2}`
