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在现实生活中,满足s=ab关系的事物非常多,如路程等于速度乘以时间,长方形的面积等于长与宽的积,电压等于电流强度乘以电阻,在这些关系中如果s=ab中a,b有一个是常量,另一个是关于x的变量,那么s就是关于x的一次函数,而当a,b都是关于x的变量时,通常s就是x的二次函数关系了,在实际中此类问题很多,应用二次函数的性质,如顶点,对称性,增减性就可以解决相关的问题.
In real life, there are many things that satisfy the s = ab relationship, such as the distance equals speed multiplied by time, the area of the rectangle equals the product of length and width, and the voltage equals the current strength multiplied by the resistance. If s = ab a, b have a constant, the other is a variable on x, then s is a function of x, and when a and b are variables on x, usually s is the quadratic function of x, and in the In fact, many such problems, the application of the nature of quadratic functions, such as vertex, symmetry, increase or decrease can solve the related problems.