当二次函数y=x²+4x+9取最小值时,的值为(   )

①二班栽树多少棵？____

②三班栽树多少棵？____

③二班和三班共栽树多少棵？____

请你选择你最喜欢的两个问题，在后面括号里打“√”，并列式解答你最喜欢的这两个问题．

地理环境是区域经济发展的基础，同时又深受人类活动的影响，区域经济发展应遵循因地制宜的原则。阅读下列材料，回答下列问题。

材料一  我国某区域图。

材料二  经专家对植被的综合研究，将造林树种分为四类：①高耗水、高水分利用率的树种，如杨树、刺槐等；②高耗水、低水分利用率、抗旱性很强的树种，如柠条等；③低耗水、高水分利用率的树种，如沙拐枣等；④低耗水、低水分利用率的树种，如油松、侧柏、狼牙刺等。

    Now more and more people in the world are getting fatter. This troubles them a lot. （1）Experts(专家) say that it has a lot to do with our eating habits.
    Our eating habits are very important for good health and a strong body. Most of us like eating sweets and ice cream better than vegetables and rice. Sweets and ice cream are not bad for us if we eat them at the end of a meal. （2）If we eat them before a meal, they may take away our appetite(食欲).
    It's important for us to eat our meal in the same period each day. When we feel worried or excited, we may not want to eat. A long time ago, in England, some judges(法官) often decided whether a man was telling the truth by giving him some dry bread. If the man could not swallow(吞) the bread, it meant that he wasn't telling the truth. Because when a man is worried about something, he will have trouble in swallowing anything dry, because he loses his appetite.

阅读表达 (阅读短文，并根据短文内容回答问题。)

    Computers are useful machines．They can help people a lot in their daily life ． For example，they can help people to save much time to do much work，and they can help people to work out many problems easily．Our country asks everyone to learn to use computers before the twenty-first century，except the old people．

    Today more and more families own computers ． Parents buy computers for their children．They hope computers can help them improve their studies in school．Yet，many of their children use computers to play games，to watch videos or to chat．Computers can not help children to study but make them fall behind．So computers are locked in boxes by parents．

    In some other countries，even some scientists also hate computers．They say computers let millions of people lose their jobs or bring them a lot of trouble．Will computers really bring trouble to people or can they bring people happiness? It will be decided by today's students themselves!