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1.已知数列{An}满足A1=1,An= 2A(n-1)+2(n∈N,且N≥2)

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1.已知数列{An}满足A1=1,An= 2A(n-1)+2(n∈N,且N≥2)
(1)求A1,A2
(2)设bn=An+2,证明数列{bn}是等比数列,并指出其首项和公比
2.已知数列{An}满足A1=-1,An+1=2An,求该数列前十项的和S10
1.(1) A1 =1,A2 = 2*A1 + 2 = 4.
(2) b(n+1) / bn =( A(n+1)+ 2) / ( An +2)
= (2An+2 +2)/(An+2) = 2; b1 =A1+2 =3;
故bn为 首项为3,公比为2 的等比数列
2.公比2,则 S10 = -1 * (1 - 2^10)/(1-2) = -1023