设数列{An}满足下列关系:a1=2a,An=2a-[a^2/(An-1)];Bn=1/(An-a),求证:(1)An≠a;(2)Bn是等差数列

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设数列{An}满足下列关系:a1=2a,An=2a-[a^2/(An-1)];Bn=1/(An-a),求证:(1)An≠a;(2)Bn是等差数列

设数列{An}满足下列关系:a1=2a,An=2a-[a^2/(An-1)];Bn=1/(An-a),求证:(1)An≠a;(2)Bn是等差数列
设数列{An}满足下列关系:a1=2a,An=2a-[a^2/(An-1)];Bn=1/(An-a),求证:(1)An≠a;(2)Bn是等差数列

设数列{An}满足下列关系:a1=2a,An=2a-[a^2/(An-1)];Bn=1/(An-a),求证:(1)An≠a;(2)Bn是等差数列
1、反证法
假设A[n]=a,那么代入等式a=2*a-(a^2/A[n-1])
得出 A[n-1]=A[n]=a
因此可以推出 A[1]=A[2]=...=A[n]=a与题中A[1]=2a矛盾
2、
B[n]-B[n-1]=(A[n-1]-A[n])/(A[n]*A[n-1]-a*(A[n]+A[n-1])+a^2)
由A[n]*A[n-1]=2*a*A[n-1]-a^2带入上式
B[n]-B[n-1]=(A[n-1]-A[n])/(a*(A[n-1]-A[n]))=1/a=常数
因此 B[n]是等差数列

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