1/1+（2/1-1/2）+(3/1-2/2+1/3)+(4/1-3/2+2/3-1/4)+…+(9/1-8/2+7/3-6/4+…+1/9)

1/1+（2/1-1/2）+(3/1-2/2+1/3)+(4/1-3/2+2/3-1/4)+…+(9/1-8/2+7/3-6/4+…+1/9)
=(1/1+2/1+3/1+4/1…+9/1）+（-1/2-2/2-3/2…-8/2）+（1/3+2/3…7/3）+…+（1/9)
=45+36/2+28/3+21/4+15/5+10/6+6/7+3/8+1/9
=45+18+28/3+21/4+3+5/3+6/7+3/8+1/9
=66+11+45/8+6/7+1/9
=77+45/8+6/7+1/9
行了 自己通分吧