老师说要做这题原文题的报告 但是我实在摸不着头绪该怎办 麻烦各位大大帮我解答一下 回覆我信箱 感谢万分~ ============================================================= It is estimated that X months from now. the population of a certain community will be P(x)=x^2(x平方)+20x+8,000 a.At what rate will the population be changing with respect to time 15 months from now? b.By now much will thw population actually change during the 16th months? Solution a.The rate of change of the population with respect to time is the derivative of the population function.That is, Rate of change = P'(x)=2x+20 The rate of change of the population 15 months from now will be p'(15)= 2+(15)+20 = 50 people per month b.The actual change in the population during the 16th month is the difference between the population at the end 16 months and the population at the end of 15 months. That is, Change in population = P(16)-P(15) =8,576-8,525 = 51 people ============================================================= 多谢各位 --

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