已知数列{An},Sn=0.125(An+2)(An+2).求证:{An}是等差数列

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已知数列{An},Sn=0.125(An+2)(An+2).求证:{An}是等差数列

已知数列{An},Sn=0.125(An+2)(An+2).求证:{An}是等差数列
已知数列{An},Sn=0.125(An+2)(An+2).求证:{An}是等差数列

已知数列{An},Sn=0.125(An+2)(An+2).求证:{An}是等差数列
由S(n-1)=Sn-An
将Sn带入,两端乘以8得:(A(n-1)+2)(A(n-1)+2)=(An-2)(An-2)
开方,有An-A(n-1)=4,所以:{An}是等差数列,公差为4,首项为2.通项公式:An=4n-2

An+2是什么啊是(An)+2,还是A(n+2)