Graphing Rational Functions Example #4 End ShowEnd Show Slide #1 NextNext We want to graph this rational function showing all relevant characteristics.

3 2x +2x - 4x - 8f(x)=

x

Graphing Rational FunctionsExample #4

End Show Slide #1 Next

We want to graph this rational function showing all relevant characteristics.

3 2x +2x - 4x - 8f(x)=

x

2(x+2) (x -2)

=x


Previous Slide #2 Next

First we must factor both numerator and denominator, but don’t reduce the fraction yet.

Numerator: Factor by groups.Denominator: It's prime.

3 2x +2x - 4x - 8f(x)=

x

2(x+2) (x -2)

=x

;x 0



Note the domain restrictions, where the denominator is 0.

3 2x +2x - 4x - 8f(x)=

x

2(x+2) (x -2)

=x

;x 0



Now reduce the fraction. In this case, there are no common factors. So it doesn't reduce.

3 2x +2x - 4x - 8f(x)=

x

2(x+2) (x -2)

=x

;x 0

V.A.:x=0



Any places where the reduced form is undefined, the denominator is 0, forms a vertical asymptote. Remember to give the V. A. and the full

equation of the line and to graph it as a dashed line.

3 2x +2x - 4x - 8f(x)=

x

2(x+2) (x -2)

=x

;x 0

V.A.:x=0 NoHoles



Any values of x that are not in the domain of the function but are not a V.A. form holes in the graph. In other words, any factor that reduced completely

out of the denominator would create a hole in the graph where it is 0.Since this example didn't reduce, it has no holes.

3 2x +2x - 4x - 8f(x)=

x

2(x+2) (x -2)

=x

;x 0

V.A.:x=0 NoHoles NoH.A.or O.A.



Next look at the degrees of both the numerator and the denominator. Because the denominator's degree, 1, is less than the numerator's, 3,by

more than 1, there is neither a horizontal asymptote nor an oblique asymptote. Thus, at the ends the graph will either curve up or curve down.

3 2x +2x - 4x - 8f(x)=

x

2(x+2) (x -2)

=x

;x 0


2Opt.:Endbehavior like y= x



Optional step: Even though there isn't a H.A. or an O.A. we can determine the end behavior of the graph. By dividing the leading terms, x3 and x, we get x2. So the end behavior of the graph of f(x) will be like that of y=x2, a

parabola that opens up.

3 2x +2x - 4x - 8f(x)=

x

2(x+2) (x -2)

=x

;x 0



x - int=-2,2



We find the x-intercepts by solving when the function is 0, which would be when the numerator is 0. Thus, when x+2=0 and x-2=0.

3 2x +2x - 4x - 8f(x)=

x

2(x+2) (x -2)

=x

;x 0



x - int=-2,2

No y- int.



Now find the y-intercept by plugging in 0 for x, but in this case that would lead to a 0 in the denominator. Thus, there can't be a y-intercept.

3 2x +2x - 4x - 8f(x)=

x

2(x+2) (x -2)

=x

;x 0



x - int=-2,2

No y- int.



Plot any additional points needed.In this case we don't need any other points to determine the graph.

Though, you can always plot more points if you want to.

3 2x +2x - 4x - 8f(x)=

x

2(x+2) (x -2)

=x

;x 0



x - int=-2,2

No y- int.



Finally draw in the curve.For x<-2, we can use that the left end behavior to know the graph has to curve up to the left of x=-2. You could also plot more points to determine

this.

3 2x +2x - 4x - 8f(x)=

x

2(x+2) (x -2)

=x

;x 0



x - int=-2,2

No y- int.



For -2<x<0, we can use the multiplicity of the x-int.=-2 is even, 2, to get that the graph has to bounce off the x-axis and then curve up on the left

the V.A. You could also plot more points instead of multiplicity.

3 2x +2x - 4x - 8f(x)=

x

2(x+2) (x -2)

=x

;x 0



x - int=-2,2

No y- int.



For x>2, we can use the right end behavior to get that the graph has to curve up to the right of x=2. You could also plot more points to determine

this.

3 2x +2x - 4x - 8f(x)=

x

2(x+2) (x -2)

=x

;x 0



x - int=-2,2

No y- int.



For 0<x<2, we can that the multiplicity of x-int.=2 is odd, 1, to get that the graph has to cross the x-axis and then curve down on the right of the V.A.

You could also plot more points instead of multiplicity.

3 2x +2x - 4x - 8f(x)=

x

2(x+2) (x -2)

=x

;x 0



x - int=-2,2

No y- int.


Previous Slide #16 End Show

This finishes the graph.

Graphing Rational Functions Example #4 End ShowEnd Show Slide #1 NextNext We want to graph this rational function showing all relevant characteristics.

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