题: (1/50-1)(1/49-1)(1/48-1)···(1/2-1)
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题: (1/50-1)(1/49-1)(1/48-1)···(1/2-1)
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(1/50-1)(1/49-1)(1/48-1)···(1/2-1)
=(-49/50)(-48/49)(-47/48).......(-1/2)
=1/50
=(-49/50)×(-48/49)×(-47/48)×…×(-2/3)×(-1/2)
=-1/50(有49个负数相加,相邻两个可以约分,约分后剩下分母50和分子1)