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问题 填空题
已知
1
a
-
1
b
=5，则
2a+3ab-2b
a-2ab-b
的值是______．
答案

由已知

1
a
-
1
b
=5，得a-b=-5ab，

则

2a+3ab-2b
a-2ab-b
=
2(a-b)+3ab
(a-b)-2ab
=
-10ab+3ab
-5ab-2ab
=
-7ab
-7ab
=1．

填空题

Kofi Annan says helping survivors of last week’ s earthquake and (1) . in the Indian Ocean is (2) . The United Nations secretary-general says countnes that have offered aid must (3) and provide it. The offers add up to around (4) dollars. Unitd Nations officials say (5) of that is needed during the next six months.
The concern about offers of international aid is (6) . For example, the earthquake in Bam, Iran, in (7) of 2003 killed more than (8) people. Countries and groups offered hundreds of millions of dollars (9) . The United Nations says it has (10) only about (11) dollars in aid received so far. Governments and organizations that offered help (12) that, however.
On (13) Mr. Annan met with world leaders in Jakarta, Indonesia to discuss aid for (14) . The leaders discussed and (15) the idea of (16) owed by affected nations. But the leaders did not say they would do so. Some said that (17) to survivors would be more helpful.
Representatives of (18) countries and international organizations attended the meeting in Jakarta. Officials say they will cooperate to develop (19) for the Indian Ocean and the (20) .
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单项选择题

气泡半径越大，熔池金属的密度（），粘度越小时，则气泡的上浮速度也就越大，焊缝中就不易产生气孔。

A、越大

B、越小

C、较小
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