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06-05-2021
01:37 PM

06-05-2021
01:37 PM

Hi, im totally newbie.

I have 2 problems and i dont know hot to solve it 😕

Any ideas ?

Solved! Go to Solution.

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06-06-2021
06:26 AM

06-06-2021
06:26 AM

@LucMeekes wrote:

The inequality:

This means: x<0 OR 0<x<3/4

Success!

Luc

What you show is the result of MC11 with Maple as symbolic engine. Unfortunately the symbolic engine was changed twice since then and the newest one (Axiom/FriCAS; the only one available in Prime 7) is not able to solve that inequality.

Here is a comparison done in Prime 6 showing of the results we get using the legacy symbolic (muPad) and the new one (Axiom/FriCAS). Interesting in both cases is the effects we get, when we simply use "solve" compared to those if we explicitly specify the variable x. There is also a big difference in the results depending on whether we are storing the derivative into a function or using it directly. Also note the effect "simplify" has on the result with the new symbolic.

Legacy Symbolic (muPad):

New symbolic (Axiom/FriCAS):

8 REPLIES 8

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06-05-2021
01:55 PM

06-05-2021
01:55 PM

Re: No solution was found

I can't do symbolics, but I can address your issues:

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06-05-2021
02:10 PM

06-05-2021
02:10 PM

Re: No solution was found

is this the only one solution? you can't solve the inequality with the "solve" method?

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06-05-2021
03:37 PM

06-05-2021
03:37 PM

Re: No solution was found

I'm constrained to Prime Express, since I don't have a license. (Express is free!) Symbolic operations (like solve) are "premium" features that Express will display but not execute, so I can see what you've done (as long as I don't resave your sheet) but I can't run it.

That said, symbolic operations never were a really strong feature in Mathcad and they have not improved in Prime. The numeric solution shows that the derivative function goes strongly positive for negative x, change the range of xx to see this. The derivative function goes to zero at x = 0, but it does not go negative until x = 3/4. So the root function (which Express will do) cannot find the root at zero, but it will find the root at 3/4. I suspect that the solve found a double root at zero because of two imaginary roots.

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06-05-2021
07:46 PM

06-05-2021
07:46 PM

Re: No solution was found

Page 2 Triple root is 0 and the f(0) = 0 with evaluate "=".

Page 4 df(x) must above the plot.

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06-06-2021
05:22 AM

06-06-2021
05:22 AM

Re: No solution was found

The inequality:

This means: x<0 OR 0<x<3/4

Success!

Luc

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06-06-2021
06:26 AM

06-06-2021
06:26 AM

@LucMeekes wrote:

The inequality:

This means: x<0 OR 0<x<3/4

Success!

Luc

What you show is the result of MC11 with Maple as symbolic engine. Unfortunately the symbolic engine was changed twice since then and the newest one (Axiom/FriCAS; the only one available in Prime 7) is not able to solve that inequality.

Here is a comparison done in Prime 6 showing of the results we get using the legacy symbolic (muPad) and the new one (Axiom/FriCAS). Interesting in both cases is the effects we get, when we simply use "solve" compared to those if we explicitly specify the variable x. There is also a big difference in the results depending on whether we are storing the derivative into a function or using it directly. Also note the effect "simplify" has on the result with the new symbolic.

Legacy Symbolic (muPad):

New symbolic (Axiom/FriCAS):

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06-06-2021
06:41 AM

06-06-2021
06:41 AM

Re: No solution was found

As described above, the new and only symbolic available in P7 is unable to solve this inequality.

According to plotting:

It works OK, if you either

- define a function for the derivative
- or if you define a range variable

I manually changed the lower limit on the abscissa to -1 in the first plot (quickplot) and in both cases the upper limit on the ordinate to 0.2.

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06-06-2021
10:07 AM

06-06-2021
10:07 AM

Re: No solution was found

Thank you! You helped me a lot. All of you. Greetings!