x/(x-1)-1/2(x-1)=3
2x-1=6(x-1) 两边同乘2(x-1)
x=5/4 经检验非增根
2/(x+1)=3/[2(x+1)]+1
4=3+2(x+1) 两边同乘2(x+1)
x=-½ 经检验非增根