[tex]f(x) = 8x + 5\,,\,\,\,g(x) = 9x-2\\(f-g)(x) = 8x+5-(9x-2) = 8x-9x + 5+ 2= -x + 7\\(f-g)(x) = -x +7[/tex]
Domain: [tex]x\in (-\infty,+\infty)[/tex]
Note: I am assuming the "f − g (f − g)(x)" in your question really meant "(f-g)(x)." If that is not the case please elaborate the question (via comments) and I will respond.
