等比数列an的前n项积为Tn a1a2a7=8 T7=
问题描述:
等比数列an的前n项积为Tn a1a2a7=8 T7=
答
a1a2a7=a1^3*q^7=8
T7=a1^7*q^21题目有误是a1a3a7还不对a2a3a7a2a3a7=a1^3*q^9=8,a1*q^3=2T7=a1^7*q^21=2^7