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变量可分为两种: 1.离散型变量,即变量的取值是有限个或可数无限个,如x∈{2,3,5,7},x∈N; 2.连续型变量,即变量的取值不可数,如x∈R,x∈[-1,1]. 解连续型变量的最值问题一般用函数法;解离散型变量的最值问题则多用比较调整法.下面借两道物理题予以说明. 例1 一个阻值为8Ω的电阻R1与一个最大阻值为24Ω的滑动变阻器R2串联,接在电压U=4V的电源上,问R2为多大时,R2消耗的电功率P2最大? 分析这是连续型最值问题,可以选
Variables can be divided into two types: 1. Discrete variables, that is, the value of the variable is a finite or countable infinite number, such as x∈{2,3,5,7}, x∈N; 2. Continuous variables, That is, the value of the variable is uncountable, such as x ∈ R, x ∈ -1 -1 -1 -1 -1 [-1, 1]. The problem of solving the maximum value of the continuous variable is generally used in the function method; the solution to the maximum value of the discrete variable is the method of comparative adjustment. Let’s explain with two physical problems. Example 1 A resistor R1 with a resistance of 8Ω is connected in series with a sliding rheostat R2 with a maximum resistance of 24Ω. It is connected to a power supply with a voltage of U=4V. When R2 is large, R2 is consumed. Electric power P2 maximum? Analysis This is a continuous value problem, you can choose