x^4 -2x^3 +2x^3-4x^2 -3x^2+6x-2x+4 = 0
x^3(x-2) +2x^2(x-2)-3x(x-2) -2(x-2) = 0
(x-2)(x^3 +2x^2 -3x -2) =0
x=2;