1. Graphing Rational Functions
LESSON 8–4
Graphing Rational Functions

2. Five-Minute Check (over Lesson 8–3) TEKS Then/Now New Vocabulary
Key Concept: Vertical and Horizontal Asymptotes
Example 1: Graph with No Horizontal Asymptote
Example 2: Real-World Example: Use Graphs of Rational Functions
Key Concept: Oblique Asymptotes
Example 3: Determine Oblique Asymptotes
Key Concept: Point Discontinuity
Example 4: Graph with Point Discontinuity
Lesson Menu

3. Which is not an asymptote of the function
A. x = –6
B. f(x) = 0
C. x = 2
D. f(x) = 4
5-Minute Check 1

4. Which is not an asymptote of the function
A. x = –4
B. x = 7
C. x = 4
D. f(x) = 0
5-Minute Check 2

5. State the domain and range of
A. D = {x | x ≠ –6} R = {f(x) | f(x) ≠ 0}
B. D = {x | x ≠ 0} R = {f(x) | f(x) ≠ 0}
C. D = {x | x ≠ –6, 0} R = {f(x) | f(x) ≠ 0}
D. D = {x | x ≠ 0} R = {all real numbers}
5-Minute Check 3

6. A. B. C. D.
5-Minute Check 4

7. For what value of x is undefined?
A. –7 and –2
B. 7 and –2
C. –7 and 2
D. 7 and 2
5-Minute Check 5

8. Mathematical Processes A2.1(E), A2.1(F)
Targeted TEKS
A2.6(K) Determine the asymptotic restrictions on the domain of a rational function and represent domain and range using interval notation, inequalities, and
set notation.
Mathematical Processes
A2.1(E), A2.1(F)
TEKS

9. You graphed reciprocal functions.
Graph rational functions with vertical and horizontal asymptotes.
Graph rational functions with oblique asymptotes and point discontinuity.
Then/Now

10. rational function vertical asymptote horizontal asymptote
oblique asymptote
point discontinuity
Vocabulary

11. Concept

12. x = 0 Take the cube root of each side. There is a zero at x = 0.
Graph with No Horizontal Asymptote
Step 1 Find the zeros.
x3 = 0 Set a(x) = 0.
x = 0 Take the cube root of each side.
There is a zero at x = 0.
Example 1

13. Step 2 Draw the asymptotes. Find the vertical asymptote.
Graph with No Horizontal Asymptote
Step 2 Draw the asymptotes.
Find the vertical asymptote.
x + 1 = 0 Set b(x) = 0.
x = –1 Subtract 1 from each side.
There is a vertical asymptote at x = –1.
The degree of the numerator is greater than the degree of the denominator. So, there is no horizontal asymptote.
Example 1

14. Graph with No Horizontal Asymptote
Step 3 Draw the graph.
Use a table to find ordered pairs on the graph. Then connect the points.
Example 1

15. Graph with No Horizontal Asymptote
Answer:
Example 1

16. B.
C. D.
Example 1

17. Use Graphs of Rational Functions
A. AVERAGE SPEED A boat traveled upstream at r1 miles per hour. During the return trip to its original starting point, the boat traveled at r2 miles per hour. The average speed for the entire trip R is given by the formula Draw the graph if r2 = 15 miles per hour.
Example 2A

18. Original equation r2 = 15 Simplify.
Use Graphs of Rational Functions
Original equation
r2 = 15
Simplify.
The vertical asymptote is r1 = –15. Graph the vertical asymptote and function. Notice the horizontal asymptote is R = 30.
Example 2A

19. Use Graphs of Rational Functions
Answer:
Example 2A

20. B. What is the R-intercept of the graph?
Use Graphs of Rational Functions
B. What is the R-intercept of the graph?
Answer: The R-intercept is 0.
Example 2B

21. Use Graphs of Rational Functions
C. What domain and range values are meaningful in the context of the problem?
Answer: Values of r1 greater than or equal to 0 and values of R between 0 and 30 are meaningful.
Example 2C

22. A. TRANSPORTATION A train travels at one velocity V1 for a given amount of time t1 and then another velocity V2 for a different amount of time t2. The average velocity is given by Let t1 be the independent variable and let V be the dependent variable. Which graph is represented if V1 = 60 miles per hour, V2 = 30 miles per hour, and t2 = 1 hour?
Example 2

23. A. B.
C. D.
Example 2

24. B. What is the V-intercept of the graph?
D. –30
Example 2

25. A. t1 is negative and V is between 30 and 60.
C. What values of t1 and V are meaningful in the context of the problem?
A. t1 is negative and V is between 30 and 60.
B. t1 is positive and V is between 30 and 60.
C. t1 is positive and V is is less than 60.
D. t1 and V are positive.
Example 2

26. Concept

27. x = 0 Take the square root of each side. There is a zero at x = 0.
Determine Oblique Asymptotes
Graph
Step 1 Find the zeros.
x2 = 0 Set a(x) = 0.
x = 0 Take the square root of each side.
There is a zero at x = 0.
Example 3

28. Step 2 Find the asymptotes. x + 1 = 0 Set b(x) = 0.
Determine Oblique Asymptotes
Step 2 Find the asymptotes.
x + 1 = 0 Set b(x) = 0.
x = –1 Subtract 1 from each side.
There is a vertical asymptote at x = –1.
The degree of the numerator is greater than the degree of the denominator, so there is no horizontal asymptote.
The difference between the degree of the numerator and the degree of the denominator is 1, so there is an oblique asymptote.
Example 3

29. The equation of the asymptote is the quotient excluding any remainder.
Determine Oblique Asymptotes
Divide the numerator by the denominator to determine the equation of the oblique asymptote.
– 1
(–) 1
The equation of the asymptote is the quotient excluding any remainder.
Thus, the oblique asymptote is the line y = x – 1.
Example 3

30. Determine Oblique Asymptotes
Step 3 Draw the asymptotes, and then use a table of values to graph the function.
Answer:
Example 3

31. Graph B.
C. D.
Example 3

32. Concept

33. Graph with Point Discontinuity
Notice that or x + 2. Therefore, the graph of is the graph of f(x) = x + 2 with a hole at x = 2.
Example 4

34. Graph with Point Discontinuity
Answer:
Example 4

35. Which graph below is the graph of ?
A. B.
C. D.
Example 4

36. Graphing Rational Functions
LESSON 8–4
Graphing Rational Functions