How to use solver to solve for 2 unknown in a linear equation?

[Mike]

How to use Excel to solve for 2 unknown in linear equation, for eg,

x + Y = 1
3x + 4Y =7

Thanks
Mike

 

[JE McGimpsey]

One way:

A1: 1
B1: 1
C1: =A1 + B1
D1: =3*A1 + 4*B1


Set Target Cell = D1
Equal to Value of 7
By changing cells: A1:B1
Subject to the Constraints: $C$1 = 1

 

[Khoshravan]

Solver. Does it mean "Goal Seak" in Excel 2003?
XL2003 does not have the "Subject to the Constraints": $C$1 = 1
Where is the "Subject to the Constraints"?

 

[Niek Otten]

No, Goal Seek is not the same as Solver.
Solver is an add-in. It has to be activated: Tools>Add-ins, check Solver

 

[Khoshravan]

Thanks. After adding will it appear in Tools menu or elsewhere? I added but
it didn't appear in tools menu.

 

[Niek Otten]

Yes, it should show in the Tools menu

 

[Khoshravan]

I installed (Add) the solver and solved the set of 2 equations by the method
mentioned by JE McGimpsey. A very nice solution and I was unaware of
handling of set of eq. by excel.
In an extension to above question, is it possible to solve let say a set of
5 equations with 5 unknowns by the same method of JE McGimpsey ? What is the
limit of solver for handling such set of eq.

 

[JE McGimpsey]

From XL Help ("Options in the Solver Add Constraint and Change
Constraint dialog boxes"):

For linear problems, there is no limit on the
number of constraints.

 

[Bernard Liengme]

Why not clear the target cell and use two constraints:
C1=1
D1=7
It really is the best way - I have a worksheet to demo this if interested
best wishes

 

[Khoshravan]

Thanks