First of all, x cannot ever equal -1 because if it does then in the original equation you'd be dividing by 0, which is not possible. anything divided by 0 is undefined.
I think the error was in the second step: x(x+1) = 2(x+1) because they didn't need to go from the first step to there. I'm assuming they multiplied both sides of the equation with (x+1) to get rid of the fraction, but since both sides have (x+1) as the denominator the (x+1) would've cancelled out instead of multiplying with the numerator.
Correction:
[tex]\frac{x}{x+1} = \frac{2}{x+1}\\(\frac{x+1}{1}) (\frac{x}{x+1}) = (\frac{2}{x+1})(\frac{x+1}{1}) \\x = 2[/tex]
as u can see, in the second step of this correction, the (x+1)s on both sides cancel out so only the numerators remain.
Hope this helps!
