若等差数列{an}的前n项和为Sn,且an-3=10(n>7),S7=14,Sn=72,则
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等差数列an的前n项和为Sn,已知Sm=a,Sn-Sn-m=b,m、n属于自然数且n>m,求Sn?
1.已知等差数列AN的前N项和为SN,且AN+SN=4 (1)求AN的通项公式(2)若(Sn+1-2)>a(sn-2)对N属于正整数总成立,求实数A的取值范围2一直等差数列AN的前N项和为SN,且S6=S12,A2
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若等差数列{an}的前n项和为Sn,且an-3=10(n>7),S7=14,Sn=72,则