题目

设x,y满足约束条件则目标函数z=x+y的最大值是 （A）3                （B） 4                （C） 6              （D）8 答案：C 【解析】不等式表示的区域是一个三角形，3个顶点是，目标函数在取最大值6。 【规律总结】线性规划问题首先作出可行域，若为封闭区域（即几条直线围成的区域）则区域端点的值是目标函数取得最大或最小值，求出直线交点坐标代入目标函数即可求出最大值.Zhang Zhaojie, a 13-year-old schoolboy in Xiamen enjoyed many snacks during Spring Festival. “I love chocolate and chips very much. They are high in sugar and fat. But I can’t help eating them,” Zhang said.Recently, an online list of favorite snacks in China became popular. It said that peanuts, walnuts and chocolate are good for our health, and jelly, potato chips and lollipops(棒棒糖) are “bad”. Almost every kid on the planet loves snacks, and they seldom care how healthy they are. Although some snacks like chocolate and candy are found everywhere, others are unique(独特的) to a country or a culture.In Japan, Matcha(抹茶) is a kind of green tea powder. It’s made from tea leaves and can be used with ice cream or cakes. In fact, Matcha originated in China but took off in Japan. Biscuits or cookies covered with chocolate are also a Japanese favorite.Potato chips and French fries are very popular in the US. They are cheap but tasty. But they are high in calories and eating too much may make you fat. Popcorn(爆米花) is another typical snack. People eat it when they are watching sports games or visiting the amusement park. Most cinemas also sell Popcorn.In the UK, many people sit down for snacks at around 4 p.m. every day. They call it “afternoon tea”. Traditional afternoon tea is biscuits and tea. People also have scones(烤饼) with jam and cream, which is probably the most classic English snack.Countries   Snacks  What it is likeJapan   Matcha ★a kind of green tea powder made from 小题1:______ ★often used with ice cream or cakesBiscuits or cookies ★usually have 小题2:______ on themThe US 小题3:_______   ★cheap and tasty Popcorn ★when watching sports games and 小题4:_______★when visiting the amusement parkThe UK  Biscuits and tea   ★the traditional afternoon tea Scones ★eaten with小题5:________________