原式=3/2*5/4*6/5*...*11/10*2/3*4/5*...*8/9 =10/9*11/10 =11/9
(1+1/2)*(1+1/4)*(1+1/6)*(1+1/8)*(1+10/1)*(1-1/3)*(1-1/5)*(1-1/7)*(1-9/1)=3/2*5/4*....*11/10*2/3*4/5.....*8/9=3/2*2/3*5/4*4/5*.....*9/8*8/9*11/10=1*1*...*1*11/10=11/10
11/9