1/1*3+1/3*5+1/5*7+……+1/49*51=0.5(1-1/3)+0.5(1/3-1/5)+0.5(1/5-1/7)+……+0.5(1/49-1/51)=0.5(1-1/3)+1/3-1/5)+1/5-1/7+……+1/49-1/51)=0.5（1-1/51）=1/2*50/51=25/51 难道是1/3+3/5+5/7+……49/51?那还写这么...