Compile error in a problem definition

hello, I meet some trouble in problem definition.
problem order(fi,dfi)=int2d(th1)(dfialphafi/M)
// -int2d(th1)(dfi
// +int2d(th1)(dfidpfipre1*(rawl-rawi))
and the software tell me that the code after “//” are wrong. The error is

who can tell me how to make it correct?

It seems non-linear problem. So first linearize it using Newtons method.

It is given here.

Also, if possible mention the governing equation.

the governing equation is like below,

in which the pfi=(6fifi-15*fi+10)*fi^3 and gfi=pow(fi,2)*pow(1-fi,2).

your gov PDE is too big but I can say, few terms of your problem are in non-linear form.

So, first, linearize them using Newton’s method then only you can solve it.

Few links will help you in linearization process:

(FreeFem++ users | Main >> Newton2)

Newton 3D

you mean to linearlize it and get a weak form? I get the equation from an article and it provides the weak form like below,
and I wrote the code based on the weak form.