Question

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Answer 1

µ±n=1ʱ£¬a₁=S₁=a£¬
µ±n¡Ý2ʱ£¬a_n=S_n-S_n-1
=[2+(n-1)(

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)n-1]-[2+(n-2)(

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)n-2]
=(n-1)(

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)n-1-(n-2)(

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)n-2
=(n-1)(

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)n-1-(2n-4)(

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)n-1
=(3-n)(

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)n-1
Áîx_n=3-n£¬y_n=(

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)n-1
Ôò{x_n}ΪµÈ²îÊýÁУ¬{y_n}ΪµÈ±ÈÊýÁÐ
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