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问题 问答题

设二元函数y=f(x，y)满足f(x，1)=0，f’y(x，0)=sinx，f"yy(x，y)=2x，则f(x，y)=______．

答案

参考答案：将f"yy的两边对y积分，得f’y(x，y)=2xy+φ(x)．由f’y(x，0)=sinx可知φ(x)=sinx，从而f’y(x，y)=2xy+sinx．
再将上式两边对y积分，有f(x，y)=xy2+ysinx+ψ(x)．
由f(x，1)=x+sinx+ψ(x)=0，知ψ(x)=-x-sinx．
故f(x，y)=xy2+ysinx-x-sinx．

单项选择题

Most people have no idea of the hard work. One of the questions that is always asked of me is (1) I became an animal collector in the first (2) .The answer is that I have always been interested in animals and zoos. According to my parents, the first word I was able to say with any (3) was not the conventional "mamma" or "daddy", (4) the word "zoo", which I would (5) over and over again with a shrill (6) until someone, in order to (7) me up, would take me to the zoo. When I (8) a little older, we lived in Greece and I had a great (9) of pets, ranging from owls to seahorses, and I spent all my spare time (10) the countryside in search of fresh specimens to (11) to my collection of pets.(12) on I went for a year to the City Zoo, as a student (13) , to get experience of the large animals, such as lions, bears, bison and ostriches, (14) were not easy to keep at home. When I left, I (15) had enough money of my own to be able to (16) my first trip and I have been going (17) ever since then. Though a collector’s job is not an easy one and is full of (18) , it is certainly a job which will appeal (19) all those who love animals and(20) .

第（9）空应选择（）

A．many

B．amount

C．number

D．supply
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单项选择题

对于规模较大的单位工程可将其中能形成（）的部分定为一个子单位工程。

A.独立使用功能

B.独立施工建造

C.独立检验评定

D.独立竣工验收
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