For example, √x=x-2, and the squares on both sides are x = x 2-4x+4, so x 2-5x+4 = 0, (x- 1)(x-4)=0, and the roots are 1 and 4.
At this time, the root of x= 1 is the added root.
When the solution x = x 2, divide both sides by x to get x= 1. At this point, the root x=0 is omitted.