原式=(1-1/2)(1+1/2)(1-1/3)(1+1/3)(1-1/4)(1+1/4)......(1-1/99)(1+1/99)(1-1/100)(1+1/100) =(1/2)[(3/2)(2/3)(4/3)(3/4)(5/4).....(98/99)(100/99)(99/100)](101/100) =(1/2)*1*1*1....*1*(101/100) =(1/2)(101/100)=101/200