a5=a1+4d,a6=a1+5d,
所以1≤a1+4d≤4,2≤a1+5d≤3,
S6=3(a1+a6)=6a1+15d
分析可得,6a1+15d=15(a1+4d)-9(a1+5d),
故-12≤S6≤42.
故答案為[-12,42]
設(shè)等差數(shù)列{an}的前n項(xiàng)和為Sn,若1≤a5≤4,2≤a6≤3,則S6的取值范圍是 _ .
設(shè)等差數(shù)列{an}的前n項(xiàng)和為Sn,若1≤a5≤4,2≤a6≤3,則S6的取值范圍是 ___ .
數(shù)學(xué)人氣:752 ℃時(shí)間:2020-05-20 15:22:11
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