Hi, I have a problem in solving a multivariable equation. This multivariable consists of several variable which is known and are insert as input intially. For example: f(x)= a*x+b*x^2+-c*x+d(x^4+e)^2, f(x)=0 and a,b,c,d,e are inputs. I wanted to get the answer x. I have tried to use fzero and fsovle, but Matlab seem to stop at the first equation when it cannot determine the value x. The error shows : X is undetermined variable or equation. Ask: Am i right to use fzero/fsolve in this case to solve this equation?