A3-A2=A1,A1 ( q^2-q^1)=A1 ,q= (1+根5)/2
代入 A3+A2=2+根号5,解得 A1= (根5 -1) /2
An= (根5 -1) /2 * [(1+根5)/2]^(n-1) = [(1+根5)/2]^(n-2)
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A3-A2=A1,A1 ( q^2-q^1)=A1 ,q= (1+根5)/2
代入 A3+A2=2+根号5,解得 A1= (根5 -1) /2
An= (根5 -1) /2 * [(1+根5)/2]^(n-1) = [(1+根5)/2]^(n-2)
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