# Bug for command Max[Function f, Number a, Number b]

Problem description: The command Max[Function f, Number a, Number b] should give the maximum point for function f between a and b. It doesn't always do that, in fact it behaves strangely at times. See "steps to reproduce bug" below for an example.

OS: Windows 10 Education, version 1809, installed 2019-02-21, build 17763.737

Java version: 8 update 221 (build 1.8.0_221-b11)

Steps to reproduce bug (or open the attached file and go to step 5):

1) Make function f(x)=x^3-x^2

2) Make sliders a and b.

3) Enter command "A=max(f,a,b)".

4) Set a=0.2 and b=1.1.

5) Point A should be at (1.1, 0.121) but instead is found at (0.2, -0.03). When the slider a is set to a=0.3, point A jumps to the expected value.

Similar problem with command Min[Function f, Number a, Number b].

In Denmark you should set a a=-0.2 and ask for: Ekstremum(f,a,b).

I don't know the english command.

It will give you Minimum and maximum.

It seems like it generally "fails" at a, if you use Max() to find a minimum or Min() to find a maximum.

Who is to blame?

The conditions on when it works are quite strict, see https://wiki.geogebra.org/e...

but condition is rigth so I have a question: does max(f,a,b) calculate local maximum or absolute maximum?

I sometimes use this trick

Thanks for your comments, much appreciated.

I might not have been completely clear on the problem, so I've made a quick video to show what I mean: http://youtu.be/W7SDONIh8VY?hd=1. There's no sound on the video, but the problem should be clear anyway. Notice the unexpected behaviour around 00:54 and 1:03. I used a different function to show that the problem is general.

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