What's the error in this equation/solution?
The correct answer should be $x = 1 ⇒ x = ±1$, right?
Here's my attempt:
For $x=-1$, I can't "come back" from the first line to $x=1$. I get $4=0$ as a result.
However, for $x=1$, I can do this procedure and find $0=0$.
All help is appreciated.