解这类问题的关键是要学会把实际问题转化为数学问题,要能熟练地用一个变量间的代数式表示出另一个变量,从而建立两个变量间的等量关系.一、确定实际问题中的函数表达式例1甲、乙两仓库要往A、B两地运送水泥.已知甲库可调出100吨水泥,乙库可调出80吨水泥;A地需70吨水泥,B地需110吨水泥,两库到A、B两地的路程和运费如下表所示. The key to solving this kind of problem is to learn to convert the actual problem into a mathematical one, and to skillfully use the algebraic expression of one variable to represent another variable, so as to establish an equal relationship between the two variables. First, determine the actual problem. The expression of the function of Example 1 A, B two warehouses to A, B to transport two cement. Known A library can be transferred to 100 tons of cement, B can be adjusted to 80 tons of cement; A need to 70 tons of cement, B to 110 tons of cement are required. The distance and freight from the two libraries to A and B are as shown in the table below.