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# 8 - 3 Graphing Rational Functions

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8-3 Graphing Rational Functions

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### 8 - 3 Graphing Rational Functions

1. 1. UNIT 4: rational functions8-3 Graphing Rational functions
2. 2. Rational Functions• Define – Rational Function: is a function with two polynomials (one in the numerator and one in the denominator)• Define- point of discontinuity: Value that makes the denominator zero. (holes / asymptotes)• Hole: point of discontinuity that can be removed (cancelled out with the numerator)• Vertical asymptote: point of discontinuity that can not be removed (doesn’t cancel with numerator)• Horizontal asymptote: determine by the degree of numerator and denominator. (more on that later)
3. 3. Graphing rational functions• When graphing rational functions you must find points of discontinuity (holes / asymptotes)1st -Factor numerator and denominator2nd – determine points of discontinuity3rd – graph by making a table ( x − 4)( x + 1) x+3 x+3 x 2 − 3x − 4 f ( x) = y= 2 g ( x) = x −5 x − 4x + 3 x−4 ( x − 3)( x − 1)V.A. when: x=5 V.A. when x=1 & x=3 Hole when x=4 x y x y x y -3 0 -3 0 0 1 1 -1 0 1 2 3 7 5 2 -5 5 6 9 3 5 1 6 7
4. 4. Practice x+6 x 2 − 3x + 2 x−3y= f ( x) = g ( x) = x+4 x−2 3 x 2 − 11x + 6V.A. x=-4 Hole: x=2 V.A. x=2/3 Hole: x=3 x −5 x+2 2xy= f ( x) = 2 g ( x) = x x − x − 12 3x − 1V.A. x=0 V.A. x=-3 V.A. x=1/3 V.A. x=4
5. 5. Horizontal asymptotes• To find horizontal asymptotes compare the degree of the numerator “M” to the degree of the denominator “N”• If M < N, then y=0 is horizontal asymptote• If M > N, then No horizontal asymptote• If M=N, then divide leading coefficients
6. 6. Horizontal asymptotes• Determine the horizontal asymptotes 2x x+3 x 2 − 3x − 4 f ( x) = y= g ( x) = x −5 ( x − 3)( x − 1) x−4 M=1 M=1 M=2 N=1 N=2 N=1 H.A. y=2 H.A. y=0 NO H.A.
7. 7. Practice V.A. Holes H.A• Pg 521 # 17-22 23-28
8. 8. Word problem • You earn a 75% on the first test of the quarter how many consecutive 100% test scores do you need to bring your test average up to a 95%? 75 + 100 xWrite a rational function. Answer: f ( x) = x +1Find when the rationalfunction will be 95% You will need to make 100% on the next 4 test to bring your test average up to a 95%
9. 9. Word problem• A Basketball player have made 5 out of the last 7 free throws. How many more consecutive free throws do they need to make to have an average of 80%? 5+ x Answer: f ( x) =Write a rational function. 7+ xFind when the rational You will need to make thefunction will be 80% next 3 free throws for average to be an 80%
10. 10. Practice word problems• Pg 521 #39,40
11. 11. Word problem• The function below gives the concentration of the saline solution after adding x milliliters of 0.5% solution to 100 milliliters of 2% solution. 100(0.02) + x(0.005) y= 100 + x• How many ML of the 0.5% solution must be added to have a combined concentration of 0.9%? Answer: (search table) X=275