3anan210an1的精選

問題詳情：已知等比數列{an}爲遞增數列,a1=-2,且3(an+an+2)=10an+1,則公比q=. 【回答】解析因爲等比數列{an}爲遞增數列,且a1=-2<0,所以公比0<q<1.又因爲3(an+an+2)=10an+1,所以3(1+q2)=10q,即3q2-10q+3=0,解得q=3或q=...