等差数列{an},a1,a2,a3,...,am的和为64,而且am-1 + a2=8,求m

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等差数列{an},a1,a2,a3,...,am的和为64,而且am-1+a2=8,求m等差数列{an},a1,a2,a3,...,am的和为64,而且am-1+a2=8,求m等差数列{an},a1,

等差数列{an},a1,a2,a3,...,am的和为64,而且am-1 + a2=8,求m
等差数列{an},a1,a2,a3,...,am的和为64,而且am-1 + a2=8,求m

等差数列{an},a1,a2,a3,...,am的和为64,而且am-1 + a2=8,求m
a1+a2+.+am=(a1+am)*m/2=[2a1+(m-1)d]m/2=64
am-1+a2=2a1+(m-1)d=8
m=16