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不等式(组)的特殊解在实际问题中有着广泛的应用,大家可以看一看.一、解集为x≤a时,最大值的应用例1小明同学游览某风景区,乘摩托艇顺流而下,然后又乘摩托艇返回原处.已知水流速度为2 km/h,摩托艇在静水中的速度为18 km/h,为了使游览时间不超过3 h,小明同学乘摩托艇最多能走多远?分析:要解决这个问题,首先要明白顺流速度=摩托艇在静水中的速度+水流速度,逆流速度=摩托艇在静水中的速度-水流速度.解:设小明同学乘摩托艇能走x km.依题意得x/(18+2)+x/(18-2)≤3.解得x≤262/3.
Inequality (group) of the special solution in practical problems has a wide range of applications, we can take a look.A solution set for x≤a, the maximum value of the application example 1 Xiaoming classmates to visit a scenic area, by motorboat downstream And then by motorboat back to the same place.It is known that the water flow rate of 2 km / h, motorboat in still water at a speed of 18 km / h, in order to make the tour time less than 3 h, Xiao Ming students by motorboat up Analysis: To solve this problem, we must first understand the downstream speed = motorboat speed in hydrostatic water flow speed, counter-current speed = motorboat in the still water speed - water flow rate. Motorboat can go x km. According to the question was x / (18 +2) + x / (18-2) ≤ 3. Solution x ≤ 262/3.