已知等比数列的公比q=1\2,且a1+a3+a5+…a99=60,则S100=快谢
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已知等比数列的公比q=1\2,且a1+a3+a5+…a99=60,则S100=快谢
已知等比数列的公比q=1\2,且a1+a3+a5+…a99=60,则S100=
快谢
已知等比数列的公比q=1\2,且a1+a3+a5+…a99=60,则S100=快谢
S(100)=a(1)+a(2)+a(3)+…+a(99)+a(100)
=a(1)+a(3)+…+a(99)+a(2)+a(4)+…+a(100)
=[a(1)+a(3)+…+a(99)]+q[a(1)+a(3)+…+a(99)]
=60+(1/2)×60
=90