1/x(x+1)+1/(x+1)(x+2)+1/(x+2)(x+3)+.+1/(x+999)(x+1000)

yingguo0768 1年前 已收到3个回答 举报
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dql_dql 幼苗

共回答了17个问题采纳率：94.1% 举报

1/x(x+1)=1/x-1/(x+1)
1/(x+1)(x+2)=1/(x+1)-1/(x+2)
...
1/x(x+1)+1/(x+1)(x+2)+1/(x+2)(x+3)+.+1/(x+999)(x+1000)
=1/x-1/(x+1)+1/(x+1)-1/(x+2)+...+1/(x+999)-1/(x+1000)
=1/x-1/(x+1000)=1000/x(x+1000)

1年前

2

冰下无涯 花朵

共回答了1375个问题 举报

1/[x(x+1)]+1/[(x+1)(x+2)]+1/[(x+2)(x+3)]+......+1/[(x+999)(x+1000)]
=[1/x-1/(x+1)]+[1/(x+1)-1/(x+2)]+[1/(x+2)-1/(x+3)]+……+[1/(x+999)-1/(x+1000)]
=1/x-1/(x+1)+1/(x+1)-1/(x+2)+1/(x+2)-1/(x+3)+……+1/(x+999)-1/(x+1000)
=1/x-1/(x+1000)
=[(x+1000)-x]/[x(x+1000)]
=1000/[x(x+1000)]

1年前

2

马元元 精英

共回答了21805个问题 举报

原式=1/x-1/(x+1)+1/(x+1)-1/(x+2)+1/(x+2)-1/(x+3)+......+1/(x+999)-1/(x+1000)
=1-1/(x+1000)
=(x+999)/(x+1000)

1年前

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