I’m new to mathematica and that is my first query, so please forgive me whether it is one thing trivial.
I’m fixing a maximisation downside, and my foc is the next:

focsm = g (sg^2 + sm (-2 + 2 fg + four fm + three sm) + sg (-1 + fg + three fm + four sm)) +
B[1 - fg - fm - sg - sm] - (fm + sm) By-product[1][B][
1 - fg - fm - sg - sm]

As you might discover, it includes the perform B[.] and its by-product. Now, for me B[.] is a generic perform, with first by-product optimistic and second by-product much less or equal than zero. I have to impose the foc equal to zero, and resolve for sm (or alternatively fm). I attempted with the command Resolve, nevertheless it does not work.

Resolve[focsm == 0, sm]

If I give a useful kind to B[.] (for instance linear), every thing works. How can I resolve this?