设等差数列{an}的奇数项的和a1+a3+a5+……+a99=S奇,
偶数项的和a2+a4+a6+……+a100=S偶,
则S偶=(a1+d)+(a3+d)+(a5+d)+……+(a99+d)=S奇+50d.
于是S100=S奇+S偶=S奇+(S奇+50d)=2S奇+25（已知d=1/2）
又S100=145,代入上式得：145=2S奇+25,不难解得S奇=60
等差数列{an}的公差为1/2,且S100=145,则奇数项的和a1+a3+a5+……a99+?
等差数列{an}的公差为1/2,且S100=145,则奇数项的和a1+a3+a5+……a99+?
数学人气：741 ℃时间：2019-10-17 07:49:49
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