Answer :

[tex]f(x)=2x-9\\\\f(p)\to substitute\ x=p\\\\f(p)=2p-9\\\\f(x+h)\to substitute\ x=x+h\\\\f(x+h)=2(x+h)-9=2x+2h-9[/tex]
[tex]f(p)=2p-9\\ f(x+h)=2(x+h)-9=2x+2h-9[/tex]