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