>>11766632brainlet...
consider the following: if x = y, we always have f(x) = f(y) for any function f. however, the opposite isn't necessarily true. in the first step, you applied f(x)=x-1 to both sides. this happens to be reversible; i.e. if x-1 = y-1 we always have x = y. however, the next step, you applied f(x)=x^2. if x^2=y^2, you do not necessarily have x = y. therefore, after solving for x from what you got from the second line, you got solutions to the second line, not solutions to the first line.
