The asymptotic limit x=4x=4 should be obvious from the expression (since division by 0 is undefined).
y=(2x)/(x-4)y=2xx−4 is equivalent to y=2/(1-4/x)y=21−4x [provided we ignore the special case x=0x=0]
As x rarr +-oox→±∞
color(white)("XXXX")XXXX4/x rarr 04x→0
and
color(white)("XXXX")XXXXy=2/(1-4/x) rarr 2/1 = 2y=21−4x→21=2
giving the horizontal asymptotic limit.
A few test values for xx, such as
color(white)("XXXX")XXXXx=0 rarr y=0x=0→y=0
color(white)("XXXX")XXXXx=2 rarr y = -2x=2→y=−2
color(white)("XXXX")XXXXx=5 rarr y=10x=5→y=10
color(white)("XXXX")XXXXx=-4 rarr y = -1x=−4→y=−1
help give shape to the graph
graph{(2x)/(x-4) [-25.3, 26, -11.27, 14.4]}