11/20方法一：(1-1/4)=1-(1/2)2 =(1+1/2)(1-1/2) (1-1/9)=1-(1/3)2=(1+1/3)(1-1/3)(1-1/16)=1-(1/4)2=(1+1/4)(1-1/4)以此类推(1-1/100)=1-(1/10)2=(1+1/10)(1-1/10)即3/2*1/2*3/4*2/3*5/4*3/4*6/5*4/5*7/6*5/6*8/7*6...