(1).a(n+1)-an/2=2^(-n),2^(-1)[an-a(n-1)=2^(-n+1)*2^(-1)=2^(-n),,┄┄ 2^(-n+1)[a2-a1/2]=2^(-1)*2^(-n+1)=2^(-n),上式两边相加得：a(n+1)-2^(-n)=n2^(-n), an=n2^(-n+1)(2). a(n+1)-an/2=2^(-n),下面等式两边同乘{[2^(n+1)-1]/2^n}得：{[2^(1+1)-1]/2^1}*[an-a(n-1)/2]=2^[-(n-1)]*{[2^(1+1)-1]/2^1}┄┄
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┄┄{[2^n-1]/2^(n-1)... |
