Need to solve this

Hi guys I need away to solve these 3 equations and get the value of a b and c

 a+b = 204
 a+b*exp(-105*c) = 192.6
 a+b*exp(-180*c) = 177.6

I have tried to use vpasolve but it gives wrong answer. What other way to use?

Answer 1

[Stephan]

I assume you want real Solutions. Then try:

syms a b c
assume ([a b c], 'real')
eq = [a+b == 204;... 
a+b*exp(-105*c) == 192.6;... 
a+b*exp(-180*c) == 177.6];
[a, b, c] = vpasolve(eq,[a b c])

Best regards

Stephan

[Abdullah Azzam]

It gives wrong output it just make a=204 and b=0 and solve for c but when you substitute the result back in ghe equations you can varify they are wrong answers

[Walter Roberson]

vpasolve() works to finite precision according to the digits() setting, and the calculations are suffering from massive loss of precision.

You can give a search range:

[A,B,C] = vpasolve(eq,[a b c],[200 230;-50 -1/2;-5 5])

Answer 2

[Alex Sha]

Hi， How about the results belows:

a: 214.703486863113

b: -10.7034868631133

c: -0.00690634104047918