点P（2，4）在直线ax+y+b=0上的射影是点Q（4，3），则a=______，b=______．
∵P（2，4），Q（4，3），
∴kPQ=
=-4-3 2-4 1 2
又由P在直线l上的射影为Q
∴直线ax+y+b=0与直线PQ垂直，
∴所求直线的斜率为2，
则所求直线的方程为：（y-3）=2 （x-4）
整理得：-2x+y+5=0
故答案为：-2；5．
We live on the earth. We use the sea around us. What do we take from the ocean? And what do we give to it? We take fishes from the ocean—millions of kilograms of fish, every year, to feed millions of people. 小题1: We take minerals(矿物) from the ocean. We can get salt by evaporating(蒸发) seawater. 小题2: Many other minerals, such as gold, can be also got from the sea, but not by simple evaporation.小题3: Seaweed(海草) becomes food of many kinds— even candy, and ice cream—as well as medicine. Believe it or not, fresh water is another gift from the sea. We can’t drink ocean water. 小题4: But ocean water becomes fresh water when the salts are removed. In the future, we will find ourselves depending more and more on fresh water from the sea. The sea gives us food, fertilizer, minerals, water and other gifts. What do we give the sea? We pollute the ocean all the time. 小题5: Throwing waste into the ocean is killing off sea life. Yet as the world population grows, we may need the sea and its gifts more than ever. We are finally learning that if we destroy our sea, we might also destroy ourselves. Hopefully, it is not too late. 根据以上内容，从下 * * 个选项中选择适当的句子还原到短文中，使短文完整与正确。将其标号在答题卡上涂黑。（每小题2分，共10分）
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