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题库 / GMATAdvanced-PS-17
A certain manufacturer uses the function C(x)=0.04x2-8.5x+25,000 to calculate the cost, in dollars, of producing x thousand units of its product. The table above gives values of this cost function for values of x between 0 and 50 in increments of 10. For which of the following intervals is the average rate of decrease in cost less than the average rate of decrease in cost for each of the other intervals?
From x=0 to x=10
From x=10 to x=20
From x=20 to x=30
From x=30 to x=40
From x=40 to x=50
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抛物线啥的太烦了。
就(y2-y1)/y1比大小好了。
81/2500>73/24919>65/28846>55/24781>49/24724
分子分母同时减小的，看分子减小的幅度大还是分母减小的幅度大判断分数是变大还是变小了。
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