等差数列中若a1003+a1004+a1005+a1006=18则该数列前2008项和

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等差数列中若a1003+a1004+a1005+a1006=18则该数列前2008项和
等差数列中若a1003+a1004+a1005+a1006=18则该数列前2008项和

等差数列中若a1003+a1004+a1005+a1006=18则该数列前2008项和
a1003+a1004+a1005+a1006
=a1+1002d+a1+1003d+a1+1004d+a1+1005d
=4a1+[(1002+1005)+(1003+1004)]d
=4a1+2*2007d=18
2a1+2007d=9
S2008=(a1+a2008)*2008/2=(a1+a1+2007d)*1004=(2a1+2007d)*1004=9*1004=9036

a1+a2008=a2+a2007=-----=a1003+a1006=a1004+a1005=18/2=9
前2008项和S2008
=(a1+a2008)*2008/2
=9036

等差数列中若a1003+a1004+a1005+a1006=18则该数列前2008项和在等差数列中,若a1003+a1004+a1005+a1006=18,则此数列的前2008项和为? 等差数列an中 a1003+a1004+a1005+a1006=2 则该数列的前2008项和为? {an}为等差数列,a1003+a1004+a1005+a1006=18,则s2008=? 等差数列｛An｝中,若A1004+A1005+A1006+A1007+A1008=10,则S2011=? 在等差数列an中,若a1004+a1005+a1006=3,则该数列的前2009项的和为?过程要详细等差数列中,a1 等差数列{An}中,a1 等差数列中、a1 等差数列{an}中,a1 等差数列{an}中,a1 等差数列{An}中,a1 等差数列{An}中,A1 等差数列an中,a1 在等差数列中,a1 等差数列{an}中,a1 等差数列{an}中,a1 等差数列an中,a1