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## Solve 4 equations simultaneously for unknowns

As the title states I am trying to solve 4 equations simultaneously for unknowns.

I would like to solve for SM, KM, and RM.

I tired all sorts of things and now here I am, admitting I need help.

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10 REPLIES 10
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## Re: Solve 4 equations simultaneously for unknowns

"Solve Block" in Mathcad Prime: https://bit.ly/36yizDl

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## Re: Solve 4 equations simultaneously for unknowns

As an alternative

Success!

Luc

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## Re: Solve 4 equations simultaneously for unknowns

Thank you very much, this is what I am looking to do.

I still need help, I get stuck trying to input four variables to symbolically solve for.

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## Re: Solve 4 equations simultaneously for unknowns

It helps to NOT define your known constants numerically BEFORE you do symbolic operations. As an alternative you might use the clearsym function (look that up in the help!).

But most of all: DO attach your worksheet, NOT only a picture.

You should be able to do this in Prime:

(I can't because I'm limited to Prime Express).

Success!
Luc

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## Re: Solve 4 equations simultaneously for unknowns

I appreciate the help very much. Here is my work sheet.

I am a rookie. The help is beyond beneficial.

I like the solution set in your original post.

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## Re: Solve 4 equations simultaneously for unknowns

You mustn't change your equations midway a topic....

Originally your 3rd equation was (according the attached .jpg):

Now you've changed it to:

That is a small, but crucial difference, since with this equation  the set of equation does not solve.

I've changed it back and partly completed the sheet to look like mine.

Try it out (I'm limited to Prime Express, I cannot check symbolics) and come back if there's still trouble.

Leaves us with the other thing: If that second form of the 3rd equation is the right one in your model, then your system cannot be solved, at least not symbolically, probably not at all.

Success!
Luc

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## Re: Solve 4 equations simultaneously for unknowns

Thank you very much, this is what I am looking to do.

I still need help, I get stuck trying to input four variables to symbolically solve for.

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## Re: Solve 4 equations simultaneously for unknowns

You have to type "solve, DeltaT,...." in the placeholder above of the arrow similar to what you see in the picture provided by Luc. Lucs picture is from real Mathcad but this also works in Prime.

In case you still have problems getting the answer you should consider posting your worksheet instead of just a picture.

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## Re: Solve 4 equations simultaneously for unknowns

I check QC or Qc and KM in your sheet and it can solve 4 unknowns.

KM, RM, SM are 10^24-25 order. However the numbers in the equations are 10^-1 order.

So only evaluate these unknowns with 5 to 6 digit, it is failed.

float,30 to solve KM is therefore requiered.

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