3.解线性规划问题, 找出约束条件和目标函数是关键,必须认真分析题目,理清头绪,量多时可以列成表格,找出所有约束条件, 列出不等式组,再结合图形求出最优解.

2. 线性规划:

　(1)满足线性约束条件Ax+By+C＞0(或＜0)的解(x,y)叫可行解; 所有可行解组成的集合叫可行域；

(2)在数学或实际中,常需要求出满足不等式组的解中,使目标函数z=ax+by取得最大值或最小值的解(x,y),(叫最优解),这里约束条件和目标函数都是x,y的一次式,所以我们把这类问题叫线性规划.

1. 二元一次不等式表示的平面区域：

在平面直角坐标系中，设有直线(B不为0)及点，则

(1)若B>0，，则点P在直线的上方，此时不等式表示直线的上方的区域；

(2)若B>0，，则点P在直线的下方，此时不等式表示直线的下方的区域；

(3) 若B<0, 我们都把Ax+By+C＞0(或＜0)中y项的系数B化为正值.

2.了解线性规划的意义,并会简单的应用

1.理解二元一次不等式表示平面区域

　A: 小作文：(5分)

话题表述：为配合"构建和谐校园，和谐班级，人人争当文明学生"的活动，作为一名中学生，你认为该做些什么？请用简短的英语写出你的建议。

要求：语言规范，字迹工整，意思完整。30-40个词。

B: 大作文：(15分)

老师让同学们讨论网上购物 (Internet shopping) 的利(advantages)与弊(disadvantages)，根据下列信息，请你代表你们组做个发言。

　好处：方便(convenience)，24小时营业，不用排队(wait in line)；不足：看不见物品，不能享受和朋友一起购物的乐趣……

要求：1. 语言流畅，规范；2. 包含提示内容，并作适当发挥；3. 80 词左右。

　(A)根据短文内容，选出一个正确答案,。(本题共10分，每小题1分)

　A lucky donkey

　Once there was a farmer who owned a donkey(驴). The donkey was now too 36._____ to work. One day, it fell into the farmer's well.

　The farmer 37._____ the crying of the donkey, but he thought neither the donkey 38.______ the well was worth the trouble of saving. So he called his neighbours 39._____. He told them what had happened and 40._____ them to help carry dirt to bury(埋) the old donkey in the well.

　At the 41._____, the donkey was very sad. But as more and more dirt hit his 42._____, an idea struck (产生于头脑中) him: he should shake it off and climb up!

“Shake it off and climb up...shake it off and climb up...shake it off and climb up!”he 43._____ himself again and again. No matter 44._____ it hurt, the old donkey fought hard to shake the dirt off and climb up!

Before long the tired old donkey had stepped 45._____ the wall of that well! The dirt hadn't buried(埋葬)him, but had helped him. It was all because of his attitude (态度) that he saved himself.

36.(　　 )A.small 　　B.young 　　C.old 　　　D.lazy

37.(　　 )A.knew 　　B.discovered 　C.listened to 　D.heard

38.(　　 )A.and 　　　B.nor 　　　　C.or　 　　　D.so

39.(　 　)A.again 　　B.there 　　　C.together 　　D.here

40.(　　 )A.asked　 　B.let 　　　　C.offered 　　D.encouraged

41.(　　 )A.first 　　　B.time 　　　C.end 　　　D.beginning

42.(　　 )A.front 　　B.back 　　　C.face　 　　　D.feet

43.(　　 )A.relaxed　 　B.said　 　　　C.told 　　　D.helped

44.(　　 )A.where　 　B.which 　　　C.what　 　　D.how

45.(　　 )A.under　 　　B.over　 　　　C.in 　　　 to

　(B)根据短文内容，用方框中所给词的正确形式填空，使短文完整、正确(每词只用一次)

What do you do to get pocket money (零花钱) from your parents? In Western 46.________, many children do chores to get pocket money. They usually start to do 47.________ at 10 years old.

School students have to do homework and 48.________ for tests. They don't have a lot of free time in the week. They often do chores at the 49.________.

Young kids only do easy chores. So they don't 50.________ much money. But that's all right. Many of them only want to 51.________ candy. And candy is cheap! They help wash up after 52.________ and feed the family cat or dog.

When they get 53.________, kids want to buy more and more things. They want things that are more expensive 54.________candy. Then they have to work harder! They often wash the family car, cut the grass, walk the dog 55.________ cook dinner. Some jobs are a good way for kids to learn new things. For example, they can learn to use a lawnmower (割草机) or how to cook. Of course, their parents help them at first.

35._______________________________________________________

34. ______________________________________________________