(x^2-2x)^2-7x^2+14x-8=0

(x^2-2x)^2-7x^2+14x-8=0

 (x^2-2x)^2-7(x^2-2х)-8=0

х^2-2x=у

у^2-7y-8=0

y1=8     y2=-1

x^2-2x=8                x^2-2x=-1

x^2-2x-8=0             x^2-2x+1=0

x1=-2     x2=4       x3=1       x4=1