If f is periodic, g is polynomial function, fgx is periodic, f2=3,  and  g4=7,  then  g6 is

From the given data, g(x) must be linear function.Hence, fx=ax+b.Also,  g2=2a+b=3   and   g4=4a+b=7.Solving,  we  get  a=2   and    b=-1.Hence,    gx=2x-1.Then,    g6=11.