Hi, i try to solve equation c in terms of other variables, and its appear the messages and the answers is not as expected. Is supposed to be beta/p^(1/sigma)? is it?

Answer 1

[Torsten]

Maybe you want to restrict the parameters to be positive (and thus real-valued):

syms beta c sigma p positive
eqn1 = beta/c^sigma - p == 0

eqn1 = 

sc1 = solve(eqn1,c)

sc1 = 

eqn2 = (beta/c)^sigma - p == 0

eqn2 = 

sc2 = solve(eqn2,c)

sc2 = 

[Muhd Jasrim]

Thank you. If the expression is -ve, the messages also appeared. May I know why?

[Torsten]

I can't tell you in this special case.

The "problem" is that the equation

z^n = 1

does not only have real, but also complex solutions.

E.g.

syms z 
eqn = z^6 == 1;
solve(eqn)

ans = 

That's what the solver tries to tells you. So if you only want the real solutions, you must somehow exclude them in advance (which I tried by the positivity assumption) or sort them out from the obtained solution afterwards (e.g. by setting l = 0 in the expression you did obtain).