Let f(x) be defined by f(x) = x/(x - 4). What is the image of f?
the graph of f(x) = x/(x-4) looks like this:
http://www.wolframalpha.com/input/?i=plot+y+%3D+x%2F(x+-+4)+for+0+to+10
the vertical line x=4 is the asymptote
http://www.wolframalpha.com/input/?i=plot+y+%3D+x%2F(x+-+4)+for+0+to+10
the vertical line x=4 is the asymptote