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本文拟通过二例介绍简单的“短时线”. [问题1]一条笔直的公路l穿过草原.公路边有一卫生站A,距离公路30千米的地方有一居民点B.A、B的直线距离是90千米(如图1).有一天,某司机驾车从卫生站送一批急救药品到居民点B.汽车在公路上的最快速度为60千米/时,而在草地上的最快速度是30千米/时.问该司机应以怎样的路线行驶,所用的时间最短,最短的时间是多少?
This article intends to introduce a simple “short-term line” through two cases. [Problem 1] A straight road passes through the grassland. There is a health station A along the road, and there is a linear distance between residential sites BA and B at a distance of 30 kilometers from the road. It is 90 kilometers (Figure 1). One day, a driver drove a batch of emergency medicine from the health station to the residential area. B. The fastest speed of the car on the road is 60 km/h, and the most on the grass The speed is 30 km/h. Ask the driver what kind of route he should use. The time spent is the shortest. What is the shortest time?