Changing a variable in a formula

[cloudwalking]

Hi,

I am really struggling with what I think is probably an easy problem but I can't seem to work out how to express this in excel.

In Cell Z1 I have the formula:

Z1=1/A1*((1+B1/C1)*D1*E1*F1/G1+H1*(F1/G1)^3+2*(1+B1/C1)*(F1/G1)^2*1/G1)

Say if I know Z1, but need to find the value of the variable expressed in G1 is there a way I can do this?

The actual formula is expressed as:

Power Equation.png

and I need to rewrite the formula as a function of T. I have been through all sorts of online help and algebraic solving websites with no progress at all.

Any help would be amazing!

many thanks!

[djapigo]

Look into Goal Seek (under What-If Analysis)

Set Cell: Z1
To value: your #
By changing cell: G1

re-post: if you have constraints, then looking into the add-in called Solver (sorry, I don't have much experience with this)

[cloudwalking]

I knew it was easy!

[djapigo]

If you have one answer, Goal Seek will work great... multiple answers could get you stuck in a loop... I'm worried with the exponents...

To mark your thread solved do the following:
- Go to the first post
- Click edit
- Click Advance
- Just below the word "Title:" you will see a dropdown with the word No prefix.
- Change to Solve
- Click Save

[cloudwalking]

Hi, I do have a problem. Is there a way of doing this kind of thing with a formula that you're aware of?

[djapigo]

There are possibly 2 ways of doing this...
1. What is this formula called? Maybe Excel has something equivalent...
2. We can use VBA to create a new formula...

Let me know what you think...

re-post: actually, there is a 3rd way and that is to solve for G1 first...
Here's how to solve for G1...
http://www.wolframalpha.com/input/?i...1%2FG%29+for+G

Hello!!!

[cloudwalking]

That's absolutely brilliant thank you! It's what I've been trying to do. My problem is that I'm not a mathmatician and I have no idea what any of that means lol! I'm guessing that the three sections are three different methods of solving the problem? The solutions seem enormous but I guess that's to be expected with 8 different variables in the equation! I have no idea where to begin with this... argh!!

[djapigo]

Sad thing is, I'm a mathematician and I don't even understand the answer!

Wolfram Alpha will ruin your math skills... it's too easy to use...

[cloudwalking]

Haha I have no hope!! I might repost to see if anyone has any experience with solver... what do you think?

[djapigo]

Did Goal Seek give you an answer? Or was Goal Seek is too simple for your complicated formula... BTW, is there a "special name" for that formula?

Have you tried or looked into VBA (coding)... look at this website to help... http://excel.kingofmath.com/?p=267

Go ahead and ask about Solver... you just might need a few constraints (like what Wolfram Alpha suggested, there are a lot of variables that need to be 0 or not 0, etc.

Good luck...