由a2+a8=2a5=8,得到a5=4
则S9=a1+a2+…+a9=(a1+a9)+(a2+a8)+…+a5=9a5=36
故答案为:36
已知等差数列{an}中,a2+a8=8,则该数列前9项和S9等于 _.
已知等差数列{an}中,a2+a8=8,则该数列前9项和S9等于 ______.
数学人气:285 ℃时间:2020-04-16 11:24:35
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