等比数列中,公比q=1/2,且a2+a4+……+a100=30,则a1+a2+……+a100+?

Question

等比数列中,公比q=1/2,且a2+a4+……+a100=30,则a1+a2+……+a100+?

Answer 1

a2＋a4＋a6＋…＋a100=q(a1＋a3＋…＋a99),则a1＋a3＋a5＋…＋a99=60,则：
a1＋a2＋a3＋a4＋…＋a100=90