Why do I can't have value for this

[Handyperson]

Is it too big??? is there any way to figure this value out ?

[JBlackhole]

1.82866...

double check this

[-MFra-]

Hi, 

Please, excuse me if I let you notice that the first exponent is 0.3 + 2 * 5 * x ^ 0.1 and not 0.3 + 2.5 * x ^ 0.1.

[Handyperson]

Hi,

that is 0.3 + 2 * 5 * x ^ 0.1 

0.3 + 10 * x ^0.1

I will change values in your file thanks

[-MFra-]

I pointed out to JXB not you.

[JBlackhole]

Because I mistyped a number. Where you have k=5 (value which multiply the whole expression for the exponential) I typed 0.5.

[-MFra-]

Hi,

the result is:

 

[Handyperson]

Oooops my mathcad is so old and I can open only files with .mcdx

Could you attach with the pictures ?

[-MFra-]

[-MFra-]

Hi,

[LucMeekes]

There are several ways to solve this, see attached.

Your guess value is way off.

I suppose the error message hints at that.

Success!
Luc

[Werner_E]

---

Your guess value is way off.

I suppose the error message hints at that.

---

The error message simply states "This variable is undefined" and tracing back does not help (we don't even get the usual "no solution found" when we do).

But you are correct that the low guess value is causing the error. The guess must be at least  37 or higher for Mathcad to be able to find a solution.

But if I understand the last reply of the OP correct he tried to tell us that he mistakenly wrote 2*5 were he should have written 2.5 (as JXB already had assumed).

[LucMeekes]

Compare with this:

https://community.ptc.com/t5/PTC-Mathcad/Need-help-solving-one-unkown-one-equation-in-mathcad/td-p/638408

And here's another (one's) attempt to solve the same equation:

https://community.ptc.com/t5/PTC-Mathcad/undefined/m-p/638504#M188139

Luc