Ta có : \frac{x-1}{x+1}=\frac{x+1-2}{x+1}=\frac{x+1}{x+1}+\frac{-2}{x+1}=1+\frac{-2}{x+1}=5\Rightarrow \frac{-2}{x+1}=4 \Rightarrow 4x+4=-2 \Rightarrow x = \frac{-3}{2}
(x-1)/(x+1) = (x+1-2)/(x+1) = (x+1)/(x+1) - 2/x+1 = 1 - 2/(x+1)=5 -2/(x+1) = 4 4x+4 = -2 x = -3/2