计算1/x(x+1)+1/(x+2)(x+1).+1/(x+2008)(x+2009)并求当x=1时,该代数式的值

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计算1/x(x+1)+1/(x+2)(x+1).+1/(x+2008)(x+2009)并求当x=1时,该代数式的值
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计算1/x(x+1)+1/(x+2)(x+1).+1/(x+2008)(x+2009)并求当x=1时,该代数式的值
计算1/x(x+1)+1/(x+2)(x+1).+1/(x+2008)(x+2009)并求当x=1时,该代数式的值

计算1/x(x+1)+1/(x+2)(x+1).+1/(x+2008)(x+2009)并求当x=1时,该代数式的值
1/x(x+1)=1/x-1/(1+x)
1/(x+2)(x+1)=1/(x+1)-1/(x+2)
.
1/(x+2008)(x+2009)=1/(x+2008)-1/(1+2009)
1/x(x+1)+1/(x+2)(x+1).+1/(x+2008)(x+2009)=1/x-1/(1+x)+1/(x+1)-1/(x+2)+.+1/(x+2008)-1/(x+2009)
=1-1/(x+2009)
1-1/(1+2009)=1-1/2010=2009/2010


因为:1/x(x+1)=1/x-1/(x+1)
所以:1/x(x+1)+1/(x+1)(x+2)+…………+1/(x+2008)(x+2009)
=1/x-1/(x+1)+1/(x+1)-1/(x+2)+1/(x+2)-1/(x+3)+....+1/(x+2008)-1/(x+2009)
=1/x-1/(x+2009)
当x=1时:1/x-1/(x+2009)=1/1-1/(1+2009)=1-1/2010=2009/2010

原式=1/x-1/(x+2009)
当x=1时,原式=2009/2010

(1/1-1/2)+(1/2-1/3)+(1/3-1/4)+......+(1/2009-1/2010)括号去了不就是1-(1/2010)=2009/2010啊

1/x(x+1)+1/(x+2)(x+1).....+1/(x+2008)(x+2009)
=1/x - 1/x+1 + 1/(x+2)-1/(x+3)……+1/(x+2008) -1/(x+2009)
=1/x - 1/(x+2009)
当x=1时,该代数式的值=1- 1/2010

原式=1/x - 1/(x+1) + 1/(x+2)-1/(x+1)……+1/(x+2008) -1/(x+2009)
=1/x - 1/(x+2009)
当x=1 时,代入1/x - 1/(x+2009)=2009/2010