System of Equations

[lxd]

How can I develop a macro that solves a system of equations using Crammer's Rule or another feasible rule. I will like the macro to be able to handle as many as 6 equations. One (very hypothetical) example just to show what I am talking about.

10x + 5y + 2z = 10

15x + 2y + 20z = 30

Need help. Thanks a lot.

 

[shg]

That problem is underdefined; you need three equations in three unknowns to solve exactly (if there is a solution). If you have more than that, it's overdefined, and you can solve for a best fit.

An example of a square system:

       --A-- --B-- --C-- D --E-- -------------------F-------------------
   1     x     y     z       w                                          
   2      10     5     2      10                                        
   3      15     2    20      30                                        
   4       5     1    12      40                                        
   5                                                                    
   6                 x   = -6.11 E6:E8: {=MMULT(MINVERSE(A2:C4), E2:E4)}
   7                 y   = 12.29                                        
   8                 z   =  4.86                                        
   9                             Check:                                 
  10                          10 E10: =MMULT(A2:C2, E$6:E$8)            
  11                          30                                        
  12                          40

 

[lxd]

Yes, you are abosuletly right. I should have given the third equation. But did you give me the general purpose macro which solves any square system of equations? Thanks again.

 

[shg]

I gave you the general-purpose formula. Why write a macro to replace a formula that executes faster than a macro ever would?

 

[lxd]

Thanks a lot for your help!!

 

[shg]

You're very welcome.

 

[lxd]

My idea was to create a user form for people with little knowledge of Excel array formulas. Just by entering values in text boxes and clicking a command button they can get results. That is why I was interested in a VB code.