解:$(3)$原方程可化为$y+1+\frac {1}{y+1}=3+\frac {1}{3},$
∴$y+1=3$或$y+1=\frac {1}{3},$
解得$y_{1}=2,y_{2}=-\frac {2}{3}。$
$ (4)$令$\frac {2x-1}{x+2}=m,$则原方程可化为$m+\frac {1}{m}=4+\frac {1}{4},$
$ $由$(2)$的规律可得$m_{1}=4,m_{2}=\frac {1}{4},$
$ $即$\frac {2x-1}{x+2}=4$或$\frac {2x-1}{x+2}=\frac {1}{4},$
解得$x_{1}=-\frac {9}{2},x_{2}=\frac {6}{7}。$
经检验,$x_{1}=-\frac {9}{2},x_{2}=\frac {6}{7}$是原方程的解。
$ $故原方程的解为$x_{1}=-\frac {9}{2},x_{2}=\frac {6}{7}。$