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问题 单项选择题

微分方程y"+2y’+y=(x+1)e-x+2x+1有一个特解y*形式为
(A) y*=x(ax+b)e-x+(cx+d)． (B) y*=(ax+b)e-x+x2(cx+d)．
(C) y*=x2(ax+b)e-x+(cx+d)． (D) y*=(ax+b)e-x+x(cx+d)．

答案

参考答案：C

解析： 因为特征方程为λ2+2λ+1=0，特征根为重根λ1=λ2=-1，所以对应于非齐次项(x+1)e-x应设特解

，对应非齐次项2x+1应设特解

，再由迭加原理知应设特解
y*=x2(ax+b)e-x+(cx+d)，
故应选(C)．

多项选择题

It is 15 years since Moises Naim coined the memoraible phrase "corruption eruption". But there is no sign of the eruption dying down. Indeed, there is so much molten lava and sulphurous ash around that some of the world’s biggest companies have been covered in it. Siemens and Daimler have recently been forced to pay gargantuan fines. BHP Billiton has admitted that it may have been involved in bribery. America’s Department of Justice is investigating some 150 companies, targeting oil and drugs firms in particular.
The ethical case against corruption is too obvious to need spelling out. But many companies still believe that, in this respect at least, there is a regrettable tension between the dictates of ethics and the logic of business. Bribery is the price that you must pay to enter some of the world’s most difficult markets (the "when in Rome" argument). Bribery can also speed up the otherwise glacial pace of bureaucracy (the "efficient grease" hypothesis). And why not The chances of being caught are small while the rewards can be big and immediate.
But do you really have to behave like a Roman to thrive in Rome Philip Nichols, of the Wharton School, points out that plenty of Western firms have prospered in emerging markets without getting their hands dirty, including Reebok, Google and Novo Nor disk. IKEA has gone to great lengths to fight corruption in Russia. What is more, Mr Nichols argues, it is misguided to dismiss entire countries as corrupt. Even the greasiest-palmed places are in fact ambivalent about corruption: they invariably have laws against it and frequently produce politicians who campaign against it. Multinationals should help bolster the rules of the game rather than pandering to the most unscrupulous players.

And is "grease" really all that efficient In a paper published by the World Bank, the authors subjected the "efficient grease" hypothesis to careful scrutiny. They found that companies that pay bribes actually end up spending more time negotiating with bureaucrats. The prospect of a pay-off gives officials an incentive to haggle over regulations. The paper also found that borrowing is more expensive for corrupt companies.
The hidden costs of corruption are almost always much higher than companies imagine. Corruption inevitably begets ever more corruption. Corruption also exacts a high psychological cost on those who engage in it. Mr Nichols says that corrupt business people habitually compare their habit to having an affair: no sooner have you given in to temptation than you are trapped in a world of secrecy and guilt. On the other hand, the benefits of rectitude can be striking. Oil giant Texaco had such an incorruptible reputation that African border guards were said to wave its jeeps through without engaging in the ritual shakedown. Moreover, the likelihood of being caught is dramatically higher than it was a few years ago. The internet has handed much more power to whistle-blowers. Every year Transparency International publishes its Corruption Perceptions Index, and its Global Corruption Barometer.
The likelihood of prosecution is also growing. The Obama administration has revamped the Foreign Corrupt Practices Act (FCPA) and is using it to pursue corporate malefactors the world over. The Department of Justice is pursuing far more cases than it ever has before. Recent legislation has made senior managers personally liable for corruption on their watch. They risk a spell in prison as well as huge fines. The vagueness of the legislation means that the authorities may prosecute for lavish entertainment as well as more blatant bribes.
America is no longer a lone ranger. Thirty-eight countries have now signed up to the OECD’s 1997 anti-corruption convention, leading to a spate of cross-border prosecutions. In February Britain’s BAE Systems, a giant arms company, was fined $ 400m as a result of a joint British and American investigation. Since then a more ferocious Bribery Act has come into force in Britain. On April 1st Daimler was fined $185m as a result of a joint American and German investigation which examined the firm’s behaviour in 22 countries.
Companies caught between these two mighty forces--the corruption and anti-corruption eruptions--need to start taking the problem seriously. A Transparency International study of 500 prominent firms revealed that the average company only scored 17 out of a possible 50 points on "anti-corruption practices. " Companies need to develop explicit codes of conduct on corruption, train their staff to handle demands for pay-offs and back them up when they refuse them. Clubbing together and campaigning for reform can also help.
This may all sound a bit airy-fairy given that so many companies are struggling just to survive the recession. But there is nothing airy-fairy about the $16 billion in fines that Siemens has paid to the American and German governments. And there is nothing airy-fairy about a spell in prison. The phrase "doing well by doing good" is one of the most irritating parts of the CSR mantra. But when it comes to corruption, it might just fit the bill.1.Explain the sentence "Indeed, there is so much molten lava and sulphurous ash around that some of the world’s biggest companies have been covered in it. "(para. 1)
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单项选择题

持手术剪的正确姿势是（）。

A、拇指和无名指分别插入剪柄的两个环中

B、拇指和中指分别插入剪柄的两个环中

C、拇指和小指分别插入剪柄的两个环中

D、拇指和食指分别插入剪柄的两个环中

E、拇指插入剪柄一环，无名指和小指插入另一环中
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