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Chapter 9: Rational Functions

Chapter 9: Rational Functions. 9.1 Inverse Variation. Direct Variation. A function of the form y = kx as x increases y increases. ( k is the constant of variation) Example : If x and y vary directly, and x = 6 when y = 3, write an equation. Inverse Variation.

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Chapter 9: Rational Functions

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  1. Chapter 9:Rational Functions

  2. 9.1 Inverse Variation

  3. Direct Variation A function of the form y = kx as x increases y increases. (k is the constant of variation) Example: If x and y vary directly, and x = 6 when y = 3, write an equation.

  4. Inverse Variation A function has the form (k is a constant) As one value of x and y increase, the other decreases.

  5. Modeling Inverse Variation Suppose that x and y vary inversely, and x = 3 when y = -5. Write the function that models the inverse variation.

  6. You Try! Modeling Inverse Variation Suppose that x and y vary inversely, and x = -2 when y = -3. Write the function that models the inverse variation.

  7. Rational Functions

  8. Identifying from a table • Does this look like direct or inverse variation? • Find the value of k: • Write the equation:

  9. You Try! Is the relationship between the variables in each table a direct variation, an inverse variation, or neither? Write then functions. 1) 2) 3)

  10. A Combined Variation has more than one relationship. EX: is read as y varies directly with x (on top) and inversely with z (on the bottom).

  11. Write the function that models each relationship. • Z varies jointly with x and y. (Hint jointly means directly) • Z varies directly with x and inversely with the cube of y • Z varies directly with x squared and inversely with y

  12. Write a function Z varies inversely with x and y. Write a function when x = 2 and y = 4 and z = 2

  13. 9.2 Graphing Inverse Variation9.3 Rational Functions

  14. Investigation Graph the following: 1. Y = 3/X 2. Y = -8/X What do you notice?

  15. Rational Functions Rational functions in the form y = k/x is split into two parts. Each part is called a Branch. If k is POSITIVE the branches are in Quadrants I and III If k is NEGATIVE the branches are in Quadrant II and IV

  16. An Asymptote is a line that the graph approaches but NEVER touches.

  17. Asymptotes From the form • The Vertical Asymptote is x = b • The Horizontal Asymptote is y = c

  18. Identify the Asymptote from the following functions. 1. 2.

  19. You Try! Identify the Asymptote from the following functions. 1. 2.

  20. Translate: • Up 3 units and Left 2 Units • Down 5 units and Right 1 unit • Right 4 units • Such that it has a Vertical asymptote of x=3 and a horizontal asymptote of y= -2

  21. Rational Functions A rational function can also be written in the form where p and q are polynomials.

  22. Asymptotes Vertical Asymptotes are always found in the BOTTOM of a rational function. Set the bottom equal to zero and solve.

  23. Find the Vertical Asymptotes for the following. 1. 2. 3. 4.

  24. Asymptotes What are the Asymptotes? Graph it, what do you notice?!

  25. There is a HOLE in the graph is when (x – a) is a factor in both the numerator and the denominator. So on the graph, there is a HOLE at 4.

  26. A graph is Continuous if it has no jumps, breaks or holes. • A graph is Discontinuous if it does have holes or jumps or breaks.

  27. Find the places of Discontinuity:

  28. Find the places of Discontinuity:

  29. Find the places of Discontinuity:

  30. Find the places of Discontinuity:

  31. 9.4 Simplifying, Multiplying and Dividing

  32. Simplest Form • A rational expression is in SIMPLEST FORM when its numerator and denominator are polynomials that have no common divisors. • When simplifying we still need to remember HOLES as points of discontinuity.

  33. Simplify: 1.

  34. Simplify: 1.

  35. Simplify: 1.

  36. Simplify: 1.

  37. Multiplying Rational Expressions • Multiply the tops and the bottoms. • Simplify.

  38. Example:

  39. Example:

  40. Dividing Rational Expressions Dividing by a fraction is the same thing as multiplying by the reciprocal. • Flip the second fraction • Multiply the tops and the bottoms. • Simplify.

  41. Dividing Example:

  42. Dividing Example

  43. 9.5 Adding and Subtracting Rational Expressions

  44. Simplify:

  45. You Try! Simplify: .

  46. A Common Denominator is also the LEAST COMMON MULTIPLE. • LCM is the smallest numbers that each factor can be divided into evenly. Finding LCM of 2 numbers • 7: • 21:

  47. Find the LCM of each pair of numbers • 4, 5: • 3, 8: • 4, 12:

  48. Unlike Denominators 1. 2.

  49. For Variables LCM: Take the Largest Exponent! Find the LCM: • x4 and x: • x3and x2: • 3x5and 9x8:

  50. 1. 2.

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