(1-1/2)(1+1/2)(1-1/3)(1+1/3)(1-1/4)(1+1/4)...(1-1/99)(1+1/99) =(1/2)*(3/2)*(2/3)*(4/3)*(3/4)*(4/5)...(98/99)*(100/99) =1/2 * 100/99 (中间项都可以约掉) =50/99o(∩_∩)o...
3
看错题了，抱歉
50/99
