一次函数与不等式联合在实际.doc

一次函数与不等式联合在实际 Data worth having From the usual study, accumulation and summary Where there is a problem, there must be some Please also criticize and correct me! Joint decision making between first function and inequality A combination of first function and inequality is a very important type of problem for solving the problem of greater profit or minimum cost or saving money Such problems often involve two different aspects of the same problem Different functional relations are listed through practical problems On the basis of the discussion of the independent variables, the most important aspects are discussed. The following are analyzed by specific examples Example 1 A and B stores sell the same appliances at the same price However, their respective preferential programs are different. A shopping mall regulations: where the purchase of more than 1000 yuan of electrical appliances The excess amount is paid by 90%; B shopping regulation: where the purchase of more than 500 yuan of electrical appliances More than 95% of the amount received. How do customers choose shopping malls to buy electrical appliances can get greater discount? Analysis: this question involves the sale of the same appliances at the same price Different preferential programs introduced Which mall is more expensive to compare? Due to the different range of concessions Therefore, according to the amount of the purchase of electrical appliances to discuss the classification. Compare where to buy more favorable Solution: the amount of electrical equipment purchased by the customer is X Yuan It was by: When 0 x 500 Can choose any one, B, two shopping malls; When 500 x 1000 Optional B mall; When x 1000 1. The net amount of the store is: y = 1000 + (x - 1000) * 0.9 (yuan); The closing amount of the store is: y B. = 500 + (x - 500) * 0.95 (yuan); If y y B. Namely: 1000 (X1000) x 0.9 x 0.95 500 (X500) 0.9x100 0.95x25 0.05x 75 X 1500 therefore When x 1500 You can choose a mall If y = y, B. Name