(x^2-2x)^2-5(x^2-2x)-6=0
(x^2-2x-6)(x^2-2x+1)=0
(x^2-2x-6)(x-1)^2=0
(x^2-2x+1-7)(x-1)^2=0
[(x-1)^2-7)](x-1)^2=0
(x-1-√7)(x-1+√7)(x-1)^2=0
x=1+√7或x=1-√7或x=1