fsolve() crash with given Interval

[parisse]

Sorry, I tried on Xcas. I forgot that on the Prime, HP decided to remove many synonyms, therefore implicitplot is not avail on the Prime. And also indices start at 0 on Xcas, and 1 on the Prime, so you must shift by 1 (on the first firmware, [] indices started at 0 in CAS, but this was confusing because they start at 1 otherwise with ()).
And you can't replace x by X and y by Y with subst because X and Y are evaled. Perhaps you can define a CAS function of 2 variables and pass it with X and Y in the advanced grapher? By the way, it shows all the limitations of the 38-like HOME screen, as soon as you want to do something that was not anticipated by the developpers.