1985+1987+1989+……+1999/1986+1988+1990+……+2000=

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1985+1987+1989+……+1999/1986+1988+1990+……+2000=

1985+1987+1989+……+1999/1986+1988+1990+……+2000=
1985+1987+1989+……+1999/1986+1988+1990+……+2000=

1985+1987+1989+……+1999/1986+1988+1990+……+2000=
按等差数列求和,分别求分子分母,有:
分子=(1985+1999)*8/2
分母=(1986+2000)*8/2
代入分式中,有,
原数=(1985+1999)/(1986+2000)=3984/3986=1992/1993