题目

China has lately been faced with serious issues of product safety. In Panama, it is said that medicine made with a poisonous chemical sickened some people. A Chinese company had identified it as diethylamide glycol （ [化]乙二醇）, a low – cost substitute commonly used in automobile antifreeze（防冻剂）.       Some countries have banned Chinese-made toothpaste containing diethylamide glycol. China has now told companies to discontinue its use, even though it says the toothpaste is safe. Another industrial chemical, melamine, was found in wheat flour used to make pet f一个长方形的面积为x2+xy，已知宽为x，则它的周长为 ．