In the graph, the equation of vertical asymptote is
x = 4
What is vertical asymptote?
A vertical asymptote is a vertical line in the graph of a function where the function approaches infinity or negative infinity as the input values approach a certain value along that line.
A vertical asymptote is a line that a function gets arbitrarily close to as the input values get larger or smaller.
Examining the graph, the curve steadily comes close to x = 4 but never gets to it