The hardest IMO problem 2 ever

In this video, we present a solution to IMO 2021/2.

00:00 Problem Statement
00:27 The idea for the solution
03:21 first part of the proof
07:57 second part of the proof

Wiki links to used statements:

branch: algebra
difficulty: 13

[Maths_.]

I am also preparing for IMO and your videos are really helpful for me
I don't know why this channel is so underrated :(
Full support from me :)
The best thing is the way you explain is awesome :)

[Bodyknock]

5:00 Unless you’re not allowed to use calculus, it seems like it would be easier to show the square root function is concave by showing its second derivative is always negative.

If f(x) = x ¹/² then f’(x) = x ⁻¹/² /2 and f’’(x) = - x ⁻³/² / 4. Note that x ⁻³/² is always positive (it’s the reciprocal of the cube of a positive square root), so the second derivative is always negative (since it’s negative that number divided by 4).

[bred]

proof by ones got subtraction where the other has addition idk man seems pretty easy to me

[Maths_.]

If you have any courses regarding IMO please let me know

[warguy]

sometimes i like watching imo explanations for fun but this one was too much for me lol