How to calculate the coefficients in equations

Hello,

Sorry if my question is too basic. I just started using MALTAB and I was wondering how can I solve these four coefficients (a-d) with the following four equations:

1) 20=(13a)*((0.2)^b)*((34)^c)*((0.2)^d)

2) 33=(12a)*((0.32)^b)*((34)^c)*((0.2)^d)

3) 12=(9a)*((0.32)^b)*((34)^c)*((0.1)^d)

4) 20=(13a)*((0.2)^b)*((34)^c)*((0.2)^d)

Thanks !

Answer 1

[the cyclist]

I would start by taking the log of each of these equations, which will give you linear equations in (a,b,c,d).

Then I would follow one of the techniques for solving linear system discussed on this documentation page.

However, I also notice that your equation (1) and (4) are the same, so it looks like you have an underdetermined system.

[Iman]

Thanks for your reply. I logged the equations and I came to this:

2.53=1.54+loga-5.069b-0.69357c-0.4814d

3.43=1.34+loga-5.069b-0.69357c-0.4814d

4.6=1.54+loga-5.069b-0.87357c-0.4814d

2.53=1.54+loga-5.069b-0.69357c-0.7814d

Then I tried this code to solve equations:

equ1='1.34+log(a)-5.069b-0.69357c-0.4814d-3.43'

equ2='1.54+log(a)-5.069b-0.69357c-0.4814d-2.53'

equ3='1.54+log(a)-5.069b-0.87357c-0.4814d-4.6'

equ4='1.54+log(a)-5.069b-0.69357c-0.7814d-2.53'

sol=solve(equ1,equ2,equ3,equ4)

and I faced this error:

Undefined function 'solve' for input arguments of type 'char'.

Error in Iman(line 5) sol=solve(equ1,equ2,equ3,equ4)

I think I'm using a wrong function.

[the cyclist]

I don't have the Symbolic Toolbox, so I'm not sure, but I think maybe you want the linsolve function.

[Iman]

thanks

[the cyclist]

The best form of thanks is accepting an answer if it helped solve your problem.