Bug with symbolic solve?

[Werner_E]

Has anybody an explanation why the symbolic solve produces that many wrong solution if used without the modifer "fully"?

May we call it a bug? Are there other examples?

[RichardJ]

May we call it a bug?

. Is there something else we might call it?

Has anybody an explanation why the symbolic solve produces that many wrong solution if used without the modifer "fully"?

Because there's a bug

[Werner_E]

Richard Jackson wrote:

May we call it a bug?

. Is there something else we might call it?

Hmm, its PTC - maybe its a feature!? PTC marketing sure can make that possible.

Has anybody an explanation why the symbolic solve produces that many wrong solution if used without the modifer "fully"?

Because there's a bug

Yes, and obviously "fully" makes the symbolics to think about its results a second time

Alan's explanation make it clear whats happening - false solutions coming from taking the equation to the power of 4.

[ValeryOchkov]

and too few solutions:

[ValeryOchkov]

I use others tools in some cases:

[Werner_E]

Valery Ochkov wrote:

and too few solutions:

Thats indeed interesting and I wouldn't have expected a different behaviour here (because its an even root exponent).

More bugs than I wanted to experience ;-(

[AlanStevens · Accepted solution]

I think it's clear enough where the extra solutions come from; Mathcad must do something like the following on solving the equation.

Alan

[Werner_E]

AlanStevens wrote:

I think it's clear enough where the extra solutions come from; Mathcad must do something like the following on solving the equation.

Thank! Yes, at least with your explanation its clear what happens.

Nevertheless a bug which should not happen.

Also intersting the different behaviour when using the fourth root instead.

I know the difference between (-1)^(1/3) and the third root of -1 (only the latter is -1) but not sure about the fourth root and how the symbolics sees it.

Werner