Practical problems of quadratic function in Junior Three 1. A shopping mall sold a refrigerator with a purchase price of 2000 yuan at 2400 yuan, with an average of 8 refrigerators sold every day. In order to cooperate with the implementation of the national policy of "home appliances to the countryside", the shopping mall decided to take appropriate degradation measures. The survey shows that for every 50 Yuan reduction in the price of this refrigerator, an average of 4 more refrigerators can be sold every day (1) Suppose that the price of each refrigerator is reduced by X Yuan, and the profit of this refrigerator is y yuan. Please write the function expression between Y and X (do not write the value range of the independent variable) (2) In order to make a profit of 4800 yuan per day in the sales of this kind of refrigerator, and at the same time make the people get benefits, how much should each refrigerator be reduced? (3) When the price of each refrigerator is reduced by how much yuan, the profit of this kind of refrigerator is the highest? What is the highest profit? 2. In order to meet the needs of accommodating tourists, a folk tourist village has opened a hotel with 100 beds. When the daily charge for each bed is 100 yuan, all the beds can be rented out. If the daily charge for each bed is increased by 20 yuan, 10 beds will be reduced correspondingly. If the daily charge for each bed is increased by 20 yuan, the number of beds initially rented out is small and the rent is high, So how much is the most appropriate charge per bed per day? Urgent need to answer, to process! Very urgent! That pro know, please write it! Thank you very much!

Practical problems of quadratic function in Junior Three 1. A shopping mall sold a refrigerator with a purchase price of 2000 yuan at 2400 yuan, with an average of 8 refrigerators sold every day. In order to cooperate with the implementation of the national policy of "home appliances to the countryside", the shopping mall decided to take appropriate degradation measures. The survey shows that for every 50 Yuan reduction in the price of this refrigerator, an average of 4 more refrigerators can be sold every day (1) Suppose that the price of each refrigerator is reduced by X Yuan, and the profit of this refrigerator is y yuan. Please write the function expression between Y and X (do not write the value range of the independent variable) (2) In order to make a profit of 4800 yuan per day in the sales of this kind of refrigerator, and at the same time make the people get benefits, how much should each refrigerator be reduced? (3) When the price of each refrigerator is reduced by how much yuan, the profit of this kind of refrigerator is the highest? What is the highest profit? 2. In order to meet the needs of accommodating tourists, a folk tourist village has opened a hotel with 100 beds. When the daily charge for each bed is 100 yuan, all the beds can be rented out. If the daily charge for each bed is increased by 20 yuan, 10 beds will be reduced correspondingly. If the daily charge for each bed is increased by 20 yuan, the number of beds initially rented out is small and the rent is high, So how much is the most appropriate charge per bed per day? Urgent need to answer, to process! Very urgent! That pro know, please write it! Thank you very much!

The first question: (1) according to the meaning of the question, we get y = (2400-2000-x) (8 + 4 ×), that is y = - x2 + 24x + 3200; (2) from the meaning of the question, we get - x2 + 24x + 3200 = 4800