题目

There are many things you can do to improve your memory. Among them are many kinds of useful ways as well as taking special care of your health.It is important that you make yourself excited to make your memory more active. You can do this by doing some new activities and by changing your daily habits. Learning a new skill helps your brain (大脑) to develop. When trying to remember something, you should pay special attention to the most important things about it. Do not allow other thoughts to enter your mind because this will reduce your chances of making right memories.An excellent way to （2010•锦州）某商场购进一批单价为50元的商品，规定销售时单价不低于进价，每件的利润不超过40%．其中销售量y（件）与所售单价x（元）的关系可以近似的看作如图所表示的一次函数．（1）求y与x之间的函数关系式，并求出x的取值范围；（2）设该公司获得的总利润（总利润=总销售额-总成本）为w元，求w与x之间的函数关系式，当销售单价为何值时，所获利润最大，最大利润是多少？