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(1)因為{an}為等比數列,所以a5/a2=q^3=27解得q=3 a1=2.所以數列{an}的通項公式為:an=2*3^(n-1) (2)Sn=2(1-3^n)/(1-3)>50解得:n>=4所以n的最小值為4.
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