# 3.7 Rational functions  (Page 2/16)

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## Vertical asymptote

A vertical asymptote    of a graph is a vertical line $\text{\hspace{0.17em}}x=a\text{\hspace{0.17em}}$ where the graph tends toward positive or negative infinity as the inputs approach $\text{\hspace{0.17em}}a.\text{\hspace{0.17em}}$ We write

## End behavior of $\text{\hspace{0.17em}}f\left(x\right)=\frac{1}{x}$

As the values of $\text{\hspace{0.17em}}x\text{\hspace{0.17em}}$ approach infinity, the function values approach 0. As the values of $\text{\hspace{0.17em}}x\text{\hspace{0.17em}}$ approach negative infinity, the function values approach 0. See [link] . Symbolically, using arrow notation

Based on this overall behavior and the graph, we can see that the function approaches 0 but never actually reaches 0; it seems to level off as the inputs become large. This behavior creates a horizontal asymptote , a horizontal line that the graph approaches as the input increases or decreases without bound. In this case, the graph is approaching the horizontal line $\text{\hspace{0.17em}}y=0.\text{\hspace{0.17em}}$ See [link] .

## Horizontal asymptote

A horizontal asymptote    of a graph is a horizontal line $\text{\hspace{0.17em}}y=b\text{\hspace{0.17em}}$ where the graph approaches the line as the inputs increase or decrease without bound. We write

## Using arrow notation

Use arrow notation to describe the end behavior and local behavior of the function graphed in [link] .

Notice that the graph is showing a vertical asymptote at $\text{\hspace{0.17em}}x=2,\text{\hspace{0.17em}}$ which tells us that the function is undefined at $\text{\hspace{0.17em}}x=2.$

And as the inputs decrease without bound, the graph appears to be leveling off at output values of 4, indicating a horizontal asymptote at $\text{\hspace{0.17em}}y=4.\text{\hspace{0.17em}}$ As the inputs increase without bound, the graph levels off at 4.

Use arrow notation to describe the end behavior and local behavior for the reciprocal squared function.

End behavior: as Local behavior: as (there are no x - or y -intercepts)

## Using transformations to graph a rational function

Sketch a graph of the reciprocal function shifted two units to the left and up three units. Identify the horizontal and vertical asymptotes of the graph, if any.

Shifting the graph left 2 and up 3 would result in the function

$f\left(x\right)=\frac{1}{x+2}+3$

or equivalently, by giving the terms a common denominator,

$f\left(x\right)=\frac{3x+7}{x+2}$

The graph of the shifted function is displayed in [link] .

Notice that this function is undefined at $\text{\hspace{0.17em}}x=-2,\text{\hspace{0.17em}}$ and the graph also is showing a vertical asymptote at $\text{\hspace{0.17em}}x=-2.$

As the inputs increase and decrease without bound, the graph appears to be leveling off at output values of 3, indicating a horizontal asymptote at $\text{\hspace{0.17em}}y=3.$

Sketch the graph, and find the horizontal and vertical asymptotes of the reciprocal squared function that has been shifted right 3 units and down 4 units.

The function and the asymptotes are shifted 3 units right and 4 units down. As $\text{\hspace{0.17em}}x\to 3,f\left(x\right)\to \infty ,\text{\hspace{0.17em}}$ and as $\text{\hspace{0.17em}}x\to ±\infty ,f\left(x\right)\to -4.$

The function is $\text{\hspace{0.17em}}f\left(x\right)=\frac{1}{{\left(x-3\right)}^{2}}-4.$

## Solving applied problems involving rational functions

In [link] , we shifted a toolkit function in a way that resulted in the function $\text{\hspace{0.17em}}f\left(x\right)=\frac{3x+7}{x+2}.\text{\hspace{0.17em}}$ This is an example of a rational function. A rational function is a function that can be written as the quotient of two polynomial functions. Many real-world problems require us to find the ratio of two polynomial functions. Problems involving rates and concentrations often involve rational functions.

The average annual population increase of a pack of wolves is 25.
how do you find the period of a sine graph
Period =2π if there is a coefficient (b), just divide the coefficient by 2π to get the new period
Am
if not then how would I find it from a graph
Imani
by looking at the graph, find the distance between two consecutive maximum points (the highest points of the wave). so if the top of one wave is at point A (1,2) and the next top of the wave is at point B (6,2), then the period is 5, the difference of the x-coordinates.
Am
you could also do it with two consecutive minimum points or x-intercepts
Am
I will try that thank u
Imani
Case of Equilateral Hyperbola
ok
Zander
ok
Shella
f(x)=4x+2, find f(3)
Benetta
f(3)=4(3)+2 f(3)=14
lamoussa
14
Vedant
pre calc teacher: "Plug in Plug in...smell's good" f(x)=14
Devante
8x=40
Chris
Explain why log a x is not defined for a < 0
the sum of any two linear polynomial is what
Momo
how can are find the domain and range of a relations
the range is twice of the natural number which is the domain
Morolake
A cell phone company offers two plans for minutes. Plan A: $15 per month and$2 for every 300 texts. Plan B: $25 per month and$0.50 for every 100 texts. How many texts would you need to send per month for plan B to save you money?
6000
Robert
more than 6000
Robert
can I see the picture
How would you find if a radical function is one to one?
how to understand calculus?
with doing calculus
SLIMANE
Thanks po.
Jenica
Hey I am new to precalculus, and wanted clarification please on what sine is as I am floored by the terms in this app? I don't mean to sound stupid but I have only completed up to college algebra.
I don't know if you are looking for a deeper answer or not, but the sine of an angle in a right triangle is the length of the opposite side to the angle in question divided by the length of the hypotenuse of said triangle.
Marco
can you give me sir tips to quickly understand precalculus. Im new too in that topic. Thanks
Jenica
if you remember sine, cosine, and tangent from geometry, all the relationships are the same but they use x y and r instead (x is adjacent, y is opposite, and r is hypotenuse).
Natalie
it is better to use unit circle than triangle .triangle is only used for acute angles but you can begin with. Download any application named"unit circle" you find in it all you need. unit circle is a circle centred at origine (0;0) with radius r= 1.
SLIMANE
What is domain
johnphilip
the standard equation of the ellipse that has vertices (0,-4)&(0,4) and foci (0, -15)&(0,15) it's standard equation is x^2 + y^2/16 =1 tell my why is it only x^2? why is there no a^2?
what is foci?
This term is plural for a focus, it is used for conic sections. For more detail or other math questions. I recommend researching on "Khan academy" or watching "The Organic Chemistry Tutor" YouTube channel.
Chris
how to determine the vertex,focus,directrix and axis of symmetry of the parabola by equations