已知x+y=9，xy=2，求yx+xy的值．_爱下问搜题

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问题解答题

已知x+y=9，xy=2，求

y

x

+

x

y

的值．

答案

∵x+y=9，xy=2，

∴x＞0，y＞0，

∴原式=

xy

x2

+

xy

y2

=

xy

x

+

xy

y

=

xy

xy

（x+y）

=

2

2

×9

=

9

2

2

．

填空题

选词填空，并注意词形变化。

make, have, get, play, appear, play

1. They've _____ three major concerts.
2. For years, they _____ _____ other people's songs.
3. Be sure not to miss them if you _____ tickets.
4. They're going to _____ on CCTV next month.
5. Have they _____ a music video?
6. Do you _____ a musical instrument?

判断题

内容耦合是耦合程度最低的耦合。