How to find a formula with two variables

Ok, your method is not great but your function is great, can you explain it in a more detail what is it supposed to do, as i don't really understand it, also how did you get the numbers in E12 and F12
Using your function but with this code:

=LINEST(C14:C27;A14:B27;TRUE;TRUE)

i did get the exact number -0,403

Then i used the same formula as above but i swapped the places of A and B and got the exact number -0,205 which is also another number from the formula

Then i used the Factors a=-0,205 and b=-0,403 to calculate A*a and B*b which gave me some numbers then i subtracted that numbers from the solution and got another variable which is variable c=100,253

Here is the solution in the attachment.

I got the exact formula for the exact numbers... now the think is i knew the formula so i pretty much reversed engineering it, anyway i am gonna post a solution here for you and maybe someone else to learn how these functions really work.

Also here is a bit more detail explanation on how it works:

A	B	C	D	E
					
					
	Example i am trying to solve				
					
13	Var A	Var B	Sullution
14	100     80	47,513		
15	90	90	45,533		
16	98	65	53,968		
17	87	76	51,79		
18	67	70	58,308		
19	60	60	63,773		
20	90	55	59,638		
21	80	50	63,703		
22	50	45	71,868		
23	77	76	53,84		
24	88	56	59,645		
25	56	90	52,503		
26	84	110	38,703		
27	112	130	24,903

Using this

=LINEST(C14:C27;A14:B27;TRUE;TRUE)

you get the number factor b

Now swat places of var A and var B

	A	B	C
			
			
	Example i am trying to solve		
			
13	Variable B	Variable A	Sullution
14	80	100	47,513
15	90	90	45,533
16	65	98	53,968
17	76	87	51,79
18	70	67	58,308
19	60	60	63,773
20	55	90	59,638
21	50	80	63,703
22	45	50	71,868
23	76	77	53,84
24	56	88	59,645
25	90	56	52,503
26	110	84	38,703
27	130	112	24,903

Using the exact formula from above on the swapped columns a and b

=LINEST(C14:C27;A14:B27;TRUE;TRUE)

you get the number factor a

Now you have 2 factor a and b Factor a*var A+factor b*var B or short A*a+B*b this is the first part of the formula now only thing we need to do is get a constant X
Solution C = A*a+B*b + X
Now all we have to do is
X= C-A*a-B*b
now we have X=100,253

And the complete formula to get C from variables A and B

C= -0,205*A-0,403B+100,253

Now if you have any comment please do comment as i find this out by poking and trying not by knowledge of how the function works, but i guess i know know and if you read this you should to.

Also this can work for any number of variables the formula calculates a factor for the variable next to the solution