问题 填空题

x人去旅游共需支出y元,若x,y之间满足关系式y="2x2" - 20x + 1050,则当人数为_____时总支出最少。

答案

分析:将y=2x2-20x+1050变形可得:y=2(x-5)2+1000,根据二次函数的最值关系,问题可求.

解答:解:由题意,旅游的支出与人数的多少有关系,

∵y=2x2-20x+1050,

∴y=2(x-5)2+1000,

∴当x=5时,y值最小,最小为1000.

点评:本题考查利用二次函数来求最值问题,将二次函数解析式适当变形即可.

阅读理解

There are some easy things you can do to protect(保护) the environment and the earth. Choose ideas from the list or come up with a few of your own.

● Plant flowers, grass or trees.

●Whenever you visit a park or beach, take away what you bring there----keep rubbish in a bag until you can put it in a dustbin (垃圾箱).

●Turn off the lights, TV sets when you leave the room. This saves (节约)a lot of electricity.

●Turn off the tap (水笼头)when you brush your teeth. You can save some water by not letting it run. Also, use a glass cup instead of a paper cup because this saves paper.

●Keep the doors and windows closed in winter to keep warm air in.

●Give your old books and magazines to a library instead of throwing them away.

●Give your old clothes to poor children you know instead of throwing them away.

●Use both sides of paper.

●Stop pouring (倒)dirty water into the rivers or the lakes nearby (附近).

●Encourage all your friends to do the same things you do to help protect the earth.

You don’t have to wait until Earth Day to do these things. Make every day Earth Day.

If everyone makes a contribution (贡献)to protecting the environment, the world will become much more beautiful.

小题1:From the above, we know that this is ____________.

A.a sign

B.a notice

C.an advertisement

D.a proposal (提议)小题2:The writer tells us _____________.

A.to throw rubbish into a dustbin

B.to pour dirty water into the river

C.to save water by letting it run while we are brushing our teeth

D.that we can’t do all these things until Earth Day小题3:We can ___________to save paper.

A.use a paper cup

B.use both sides of paper

C.give old books to a library

D.pick up waste paper at school小题4:Which of the following is WRONG according to the writer?

A.Turn off the lights when you leave the room.

B.Close the doors in winter.

C.Use a paper cup when you brush your teeth.

D.Give your old clothes to the poor children.小题5:The main idea of this passage is how to _________.

A.save money

B.save water and electricity

C.make better use of old things

D.protect the earth

多项选择题