More Examples on Rational Functions

We would like to investigate the graph of tex2html_wrap_inline38 when P(x) and Q(x) are polynomials with the same degrees.

Example 1: Investigate the graph of tex2html_wrap_inline44

(1) First, notice that the vertical asymtote for f is x=-1.

Case 1: As tex2html_wrap_inline50 say x=-0.999, tex2html_wrap_inline54

Case 2: As tex2html_wrap_inline56 say x=-1.001, tex2html_wrap_inline60

(2) Notice that the horizontal asymtote of f is y=2 (compare the ratio between numerator and denominator.)

Case 1; As tex2html_wrap_inline66 say x=100,000, tex2html_wrap_inline70 which means that the graph will approach the horizontal line y=2 from below.

Case 2; As tex2html_wrap_inline74 say x=-100,000, tex2html_wrap_inline78 which means that the graph will approach the horizontal line y=2 from above. Use the following Maple syntax:

plot((2*x-1)/(x+1),x=-2..2, thickness=3);

to verify your answer.

Example 2: Let tex2html_wrap_inline82 Graph f.

(1) The vertical asymtotes for f are x=1 and x=2.

Case 1: As tex2html_wrap_inline92 say x=1.0001, tex2html_wrap_inline96

Case 2: As tex2html_wrap_inline98 say x=0.9999, tex2html_wrap_inline102

Case 3: As tex2html_wrap_inline104 say x=2.0001, tex2html_wrap_inline108

Case 4: As tex2html_wrap_inline110 say x=1.9999, tex2html_wrap_inline114

(2) The horizontal asymtote for f is y=1.

Case 1: As tex2html_wrap_inline66 say x=100,000, tex2html_wrap_inline124 which means the graph of f approaches to y=1 from above.

Case 2: As tex2html_wrap_inline74 say x=-100,000, tex2html_wrap_inline134which means the graph of f approaches to y=1 from below.

(3) (harder questions): Can you find the x- intercepts and find the intervals where f(x)>0 and f(x)<0.

(4) Use the folloing Maple syntax:

plot((x^2-2)/((x-1)*(x-2)),x=-2..4,y=-10..10, thickness=3);

to check your answer.