solving system of equation with mathcad prime 2

Forum|Forum|12 years ago
June 4, 2013
4 replies
7755 views

Right now my mathcad is crashed but i will type the general format

I'm having issues with the following solve block, any pointers?

guess: X1:=0.1 X2:=0.1 X3:=0.1 X4:=0.1

Constraint: Tmp = 4100/(300-ln(X1))

Tmp= 6600/(500-ln(X2))

Tmp = 7000(450-ln(X3))

Tmp = 4100/(280-ln(X4))

x1+x2+x3+x4=1

Result:

T:=find(X1,X2,X3,X4)

I keep getting no solve. What am i doing wrong? I will attach a file when I can if my mathcad comes back up

Other

Best answer by AlanStevens

What was your error message? If I write the system exactly as you have it it still works! Try going to Calculations Menu and press Calculate.

Alan

PS Uploading worksheet is better than just inserting an image. In top right-hand corner of editor is "Use advanced editor". At the bottom of the advanced editor you can insert worksheets.

W

Werner_E

25-Diamond I

Five equations but only four variables to solve for!!

A

AlanStevens

19-Tanzanite

Also, since one of your constraints is that your x's sum to unity, you might want to make your initial guesses do the same.

Alan

A

AndyWesterman

12-Amethyst

It needs 2 changes:

1 recast the equations so that you don't have the tmp variable (You aren't "finding" that anyway) ,

2 change the guess values (x1& x2 as a minimum to 0.2 ( find won't always be able to converge to a solution so you need to experiment)

regards

Andy

P

ptc-4610209

Author

1-Visitor

Thank you all so much, I much closer to getting this now, but still having issues with x4. below is my sheet that I've been working from if any of you care to take a look, I keep changing my guess for x4 but cannot seem to get it to work...

P

ptc-4610209

Author

1-Visitor

And the above are the actual equations i'm using, the ones I wrote before were just simplified examples so i didn't have to write out equations. Thank you all again for your input, I'm still learning how to use this tool.