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HP Prime Solve command at exp-Fkt. often does not work
04-05-2019, 06:15 PM
Post: #1
HP Prime Solve command at exp-Fkt. often does not work
Hello,


I have big problems solving exponential equations in CAS mode with the Solve command.

1 E.g. the equation (x^2-16)*exp(-0,5*x) has x1=4 and x2=-4 as solution. I don't get a solution from Prime.

It works very well (x^2-16)exp(x), it even works with a fraction instead of -0,5, but not with -0,5.

I have tried a lot and have no idea anymore. What am I doing wrong?

best regards
J├╝rgen
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04-06-2019, 05:31 AM
Post: #2
RE: HP Prime Solve command at exp-Fkt. often does not work
(x^2-16)*exp(-0.5*x) is an approx equation because 0.5 is an approx number, you can solve it with the approx solver:
fsolve((x^2-16)*exp(-0.5*x))
If you want to use the exact solver, convert 0.5 to an exact coefficient and run solve:
solve((x^2-16)*exp(-1/2*x))
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04-07-2019, 09:30 AM
Post: #3
RE: HP Prime Solve command at exp-Fkt. often does not work
Thank you very much for your answer!

Yes, fsolve finally solves it, but only under protest with a strange error message. The command Zero again leads to no result.
With parameters it gets even worse, example follows...

kindly regards
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