LC04 Graphing the function 

with particular attention to the vicinity of x = 3.

From past experience there is a vertical asymptote at x = 3. This asymptote line should be placed on the graph. Now use the language of limits to describe the function in the vicinity of x = 3.

                                       As x→3+,  y→+¥  As x→3−,  y→−¥

There is an additional complication as x becomes large, either positive or negative. For large x the function becomes large number over large number. If, however, the fraction is multiplied by 1/x over 1/x the limit can be calculated easily as:

This limit produces a horizontal asymptote. This asymptote line should be placed on the graph.  Now how does the curve approach this horizontal line.  When x is greater than 3, the function is positive, and when x approaches 3 from the positive side the function becomes very large, remaining positive. As x approaches 3 from the negative side the function is a large negative number. When x = −2, the function is zero and for numbers less than −2 The function is positive and approaches the horizontal asymptote from below.

As the powers in the polynomials become larger, the functions get harder and harder to graph with limit techniques. Calculus, however, provides tools for graphing higher power polynomials.  See the section of Graphing with Calculus.