In the math problem of the college entrance examination, I want to ask why the red line takes this value, can you draw a yellow line to help understand, and how did the purple line come from? thank you I'll give you a value, you take b = 1- root (e/a), the formula just looks complicated, and then let m= root (e/a), m∈(0, +∞), this function about m is increasing, which is greater than the function value when m=0, and this is enough.

After substituting into the calculation, f(b) is just greater than 0, and the value given by the standard answer is for scaling, so many restrictions are added. I don't advise you to do this. Kind of like a castle in the air. My point of view is based on methods. You can find this point if you can draw a picture and then draw a rough function diagram according to the derivative. One function is (x-2) e x, and the other is -a (x) I drew you a picture, you can understand it.

Just calculate -a (x- 1) 2 =-e and take the point of x < 1, which is the point we are looking for.

I have encountered this problem in high school before, but many of my classmates don't care about the drawing of derivative and don't consider the combination of numbers and shapes, so it is difficult to do it, and derivative is just a great weapon to describe the behavior of functions.

The picture is below, you can ask questions if you can't.