å 为1/[â(n+1)+ân]
=[â(n+1)-ân]/[â(n+1)+ân]*[â(n+1)-ân]
=â(n+1)-ân
æ以ï¼æ ¹å·2+æ ¹å·1åä¹1+æ ¹å·3+æ ¹å·2åä¹1+æ ¹å·4+æ ¹å·3åä¹1...+æ ¹å·2005+æ ¹å·2004åä¹1ï¼ï¼æ ¹å·2005+1ï¼
=(â2-â1+â3-â2+â4-â3+...â2005-â2004)(â2005+1)
=(â2005-1)*(â2005+1)
=2005-1
=2004
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