Question

2x1/3+3x1/4+4x1/5+````````+49x1/50等于多少?

Answer 1

我发现计算量有点大的哦 2x1/3+3x1/4+4x1/5+````````+49x1/50 =2/3+3/4+4/5+```````+49/50 =1-1/3+1-1/4+1-1/5+````+1-1/50 =48-(1/3+1/4+```+1/50) =48-2(3+4+```+49+50)/(50!) =48-2544/(50!)