等差数列题等差数列an的前n项和为Sn,已知am-1 + am+1 -am^2 =0,S2m-1=38,则m=

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等差数列题等差数列an的前n项和为Sn,已知am-1+am+1-am^2=0,S2m-1=38,则m=等差数列题等差数列an的前n项和为Sn,已知am-1+am+1-am^2=0,S2m-1=38,则

等差数列题等差数列an的前n项和为Sn,已知am-1 + am+1 -am^2 =0,S2m-1=38,则m=
等差数列题
等差数列an的前n项和为Sn,已知am-1 + am+1 -am^2 =0,S2m-1=38,则m=

等差数列题等差数列an的前n项和为Sn,已知am-1 + am+1 -am^2 =0,S2m-1=38,则m=
am^2=am-1+am+1
am^2=am-d+am+d
am^2=2am
am=2=a1+（m-1)d
S2m-1=(2m-1)a1+(2m-1)(2m-2)d/2
=(2m-1)a1+(2m-1)(m-1)d
=(2m-1)[a1+(m-1)d]
=(2m-1)am
=(2m-1)*2=38
2m-1=19
m=10

n?m到底是哪个

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