洋葱浏览器手机:计算1/x(x+1)+1/(x+1)(x+2)…+1/(x+1998)(x+1999)
来源:百度文库 编辑:高校问答 时间:2024/04/29 04:56:34
这到题得用到一个公式1/x(x+1)=1/x-1/(x+1)
所以原式等于1/x-1/(x+1)+1/(x+1)-1/(x+2)+......+1/(x+1998)-1/(x+1999)
正,负向抵消得1/x-1/(x+1999)
原式=1/x-1/(x+1999)
1999/x(x+1999)
原式=1/x- 1/(x+1)+ 1/(x+1)-1/(x+2)……-1/(x+1998)+ 1/(x+1998)- 1/(x+1999)=1999/x(x+1999)
结果应该是:1999/x(x+1999)
此题用推算法,你先把两组和三组数通分一下,总结出它的规律。
大哥,这么辛苦也给点分吧。
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