Step-by-step explanation:
f(x)=17-5x
if x=x+h then you can insert x+h for x in the equation of f(x)
f(x)=17-(x+h)-5x
distrubute and simplify
f(x)=17-6x-h
So that line contains the points where 17-5x and x+h intersect.
Hope that helps :)