HP 50G "Bad Argument Value"

07232017, 08:05 PM
Post: #1




HP 50G "Bad Argument Value"
SOLVE(X^40=13^X,X) > SOLVE Error: Bad Argument Value.
How to solve the equation? 

07242017, 05:01 AM
Post: #2




RE: HP 50G "Bad Argument Value"
I'd suggest using the numeric solver (ROOT) instead of SOLVE or SOLVEVX because those use CAS logic to look for a symbolic result. ROOT uses numeric methods to find one root at a time near a given initial guess.
In RPN mode: 'X^40=13^X' 'X' 1 (or whatever guess you want to start at) ROOT > 1.07109628939 With an initial guess of 1 you get another root, 0.941418703497 Also try an initial guess of 65. Finding ALL the roots is left as an exercise for the student. ;) <0ΙΈ0> Joe 

07242017, 05:32 PM
Post: #3




RE: HP 50G "Bad Argument Value"
You can also use the interactive numerical solver:
Red Shift NUM.SLV, then select 1. Solve equation (Initial guesses can be entered for X before selecting F6:SOLVE) This is useful if you want to quickly try just a few guesses. However, the ROOT command can be used in a program (for example if you wish to create a program that tries a several guesses (for instance it has an input for both the equation and a list of guesses)). 

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