x ={-(2/9)*sqrt(21), 0, (2/9)*sqrt(21)}

Let Cuberoot(1+x) =A, Cuberoot(1-x) = B

then A + B= k [k is an integer]
A³ + B³ = 2
A³ + (k- A)³ = 2

We will get quadratic equation.
And by means of discriminant; 0< k³ < 8

k =1, 2

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