Have a look at this irrational equation
Its domain is [1;+infty).
The main math packages (Derive, Maple and Mathematica) we have here, at school, give x = 0 and x = 2, both as solutions!
Actually if you square twice, at last you get:
x² - 2x = 0
that leads to x = 0 and x = 2, but x = 0 IMHO is not a solution...
What do you think about?