goal seek - grrr

[cmhoz]

I have a file that used goal seek.... usually, it works exactly as intended. However, in some situations, goal seek is finding a NEGATIVE NUMBER solution, which is technically correct, but there is also a POSITIVE NUMBER solution, which is the number I actually want.

Is there ANY WAY to tell Goal Seek to please show only positive results???

I have increased the iterations - but the trouble is that the negative number comes first in goal seek's seeking process, so it never gets to the higher iteration to show me the positive one.

Help??

 

[cmhoz]

hmm. okay. a bit more searching and it seems that there is SOME way to tell the goal seek what number to begin seeking at.

i could use this - if the seek doesn't find the answer i'm after, tell it to start over and begin at a different number...

... but i don't know how to make it start at a different number....

 

[pgc01]

Hi cmhoz

The cell that Goal Seek changes is the seed for the convergence method.

Ex.:

In B1
=A1^2-4

Let's say you want to find the values in A1 that make B1=0. This is a simple equation x^2-4=0, the roots are +2 and -2.

1 - set A1 to 10

Use Goal Seek
- Set Cell: B1
- To value: 0
- By changing cell: A1

You'll get the root (final value of A1): +2

2 - Set A1 to -10

Repeat the process.

You'll get the root (final value of A1): -2


So try different values for the changing cell, to get other solutions for your problem.