[1/（x+1）]*{（x-1）/（x+3）}+1]
=[1/（x+1）]*{ [（x-1）+（x+3）] /（x+3）}
=[1/（x+1）]*[2(X+1)/(X+3)]{ [（x-1）+（x+3）] /（x+3）}怎么等于[2(X+1)/(X+3)]1/（x+1）]*{（x-1）/（x+3）+1}=1/（x+1）]*{（x-1）/（x+3）+(x+3)/(x+3)}=1/（x+1）]*{ [（x-1）+（x+3）] /（x+3）}=1/（x+1）]*{ [2x+2] /（x+3）}=1/（x+1）]*[2(X+1)/(X+3)]你那个大括号应该位置错了，在最末尾