[VA] Short & Sweet Math Challenge #25 "San Valentin's Special: Weird Math"

[C.Ret]

Ah! Ah!

Many Thanks to Valentin for this good puzzle and the good explanation and pointing out the fact that the graph is not exactly a circle.

I didn't notice it and was wandering why I was unable to factorize Po(x,y) even with the correct equation of the expected, but outfitted circle equation.

By the fact, checking whenever the graph is or isn’t a true circle is so easy by entering its equation in the Advanced Graphic Application of the HP Prime and zoom enough to get a good view of the disparity:

   
Fig.: Po(x,y) black Circle green.


How Can I have miss verifying this weird fact ?