某商店在最近30天内的价格f（t）与时间t（单位天）的关系是f（t）=t+10（0＜t≤30，t∈N），销售量g（t）与时间t的函数关系是g（t）=35-t（0＜t≤30，t∈N），这个商店日销售金额的最大值是______．
∵价格f（t）与时间t（单位天）的关系是f（t）=t+10（0＜t≤30，t∈N），
销售量g（t）与时间t的函数关系是g（t）=35-t（0＜t≤30，t∈N），
∴日销售金额y与时间t的函数关系是y=（t+10）•（35-t）=-t2+25t+350（0＜t≤30，t∈N），
由于二次函数y=-t2+25t+350在t=
时取最大值25 2
而0＜t≤30，t∈N
∴当t=12或13时，这个商店日销售金额取最大值506
故答案为：506
In China, if people have a cold and they don’t think it’s serious, 小题1: There they can buy the medicine they need. They can also get some advice about their illnesses from the doctors and they are told what they should do. 小题2: If their illnesses are a little more serious. 小题3: Doctors usually ask about their trouble, check them over with equipments（仪器）and then give them a prescription（处方）. 小题4: they may have to stay in hospital. When people, especially（特别）the old or the babies, are badly ill, they can call 120 for help. the ambulance（救护车）can take them to the hospital as soon as possible. 小题5:
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