liward234
幼苗
共回答了21个问题采纳率:95.2% 举报
由|ab-2|与(b-1)2知道
b = 1
a = 2
b =a - 1
1/ab+1/(a+1)(b+1)+1/(a+2)(b+2)+...+1/(a+2005(b+2005)
= 1/a(a-1) + 1/(a+1)a + 1/(a+1)(a+2)+...+1/(a+2004)(a+2005)
= 1/(a-1) - 1/a + 1/a - 1/(a+1)+...+1/(a+2004) - 1/(a+2005)
=1/(a-1) - 1/(a+2005)
= 1 - 1/2007
= 2006/2007
1年前
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