高中代数上册课本复习参考题一中有这样一道习题:“写出二次函数y=ax~2+bx+c(a>0)的单调区间,以及在每一个单调区间上,函数是增函数还是减函数。”这道题的解法并不困难,同学们先画出函数y=ax~2+bx+c(a>0)的图象,结合图象直观地写出:在区间(-∞,-b/2a)上,y是减函数;在(-b/2a,+∞)上,y是增函数。 In the high school algebra book textbook review, there is an exercise such as: “Write a monotonic interval of the quadratic function y=ax~2+bx+c(a>0), and in every monotonic interval, the function is an increasing function. Or reduce the function.” The solution of this question is not difficult. The students first draw the image of the function y=ax~2+bx+c(a>0) and combine the image to write intuitively: in the interval (- On ∞,-b/2a), y is a decreasing function; on (-b/2a,+∞), y is an increasing function.