That is an undefined value. In the above equation, the denominator is x-1. As in this case, if there is a resriction on the domain, an asymptote is used. These are discussed in the next section. Since x cannot equal 1, its values are all real numbers infinitely approaching one, but not ever reaching one.
Asymptotes therefore dictate the shape of the graph.
Rational functions, however, have a more complicated formula for finding horizontal asymptotes. If the highest powers of the numerator and denominator are equal, the horizontal asymptote is the coefficient of the highest power in the numerator divided by the coefficient of the highest power of the denominator. If the highest power of the numerator is greater than the highest power in the denominator, there is no horizontal asymptote. The slant asymptote is derived by dividing the numerator by the denominator.