That is, x 3+3x2+3x2 = 0.

Because (x+1) 3 = x3+3x2+x+3x+1.

So x3+3x2+3x2 = (x+1) 3+1= 0.

That is, (x+ 1) 3 =- 1.

So X+ 1=- 1.

The solution is X=-2.