if I can not use sim as I can declare a variable?

I can not use symbolic math toolbox because when I make my executable guide I will not be able to use its functions, but I need to declare a variable because in the end my program will print a polynomial what can I do?

y=b0+b*(x-str2double(get(handles.edit8,'string')))+k*(x-str2double(get(handles.edit8,'string')))*(x-str2double(get(handles.edit11,'string')))+m*(x-str2double(get(handles.edit8,'string')))*(x-str2double(get(handles.edit11,'string')))*(x-str2double(get(handles.edit13,'string')))+f*(x-str2double(get(handles.edit8,'string')))*(x-str2double(get(handles.edit11,'string')))*(x-str2double(get(handles.edit13,'string')))*(x-str2double(get(handles.edit15,'string')))+i*(x-str2double(get(handles.edit8,'string')))*(x-str2double(get(handles.edit11,'string')))*(x-str2double(get(handles.edit13,'string')))*(x-str2double(get(handles.edit15,'string')))*(x-str2double(get(handles.edit17,'string')))