原式=1-1/2+1/2-1/3+1/3-1/4+……+1/99-1/100 =1-1/100 =99/100
1/1*2+1/2*3+1/3*4+.+1/99*100=1-1/2+1/2-1/3+1/3-1/4.+1/99-1/100=1-1/100=99/100
