Help with writing equation for fit

hello sorry this is my first post here, i really help with this

i have been given some macros which i added to plot a graph,
then i have been told to fit the graph, which i was able to do; and it came out as
" TF1 *gt = new TF1(“gt”,“gaus(0)+gaus(3)+pol1(6)”,4800,5966); "
and i obtained 8 parameters,

now i am asked to write my fit in this term
" N [F1gaus(0) + F2gaus(3)+(1-F1-F2)pol1(6)] '
N = total number of entries
F1 and F2 are the fractions for the event species.

i am using Unix operating system, and im not really good with c++ so i need a simple answers,

thank you