Question

(x-1)^4-2(x-1)^2-3=0

Answer 1

(x - 1)^2 = t ==>
t^2 - 2t - 3 = 0 
(t - 3) (t + 1) = 0 
t = 3;
t = - 1 

(x - 1)^2 = 3 
(x - 1)^2 - √3^2 = 0 
(x -1  - √3) (x - 1 + √3) = 0 
x1 = 1 + √3;
x2 = 1 - √3