# Horizontal asymptote

##### Intros
###### Lessons
1. Introduction to Horizontal Asymptote

• Horizontal Asymptotes define the right-end and left-end behaviors on the graph of a function.

• 3 cases of horizontal asymptotes in a nutshell…
##### Examples
###### Lessons
1. Algebraic Analysis on Horizontal Asymptotes

Let's take an in-depth look at the reasoning behind each case of horizontal asymptotes:

1. Case 1:

if: degree of numerator < degree of denominator

then: horizontal asymptote: y = 0 (x-axis)

$i.e. f(x) = \frac{ax^{3}+......}{bx^{5}+......}$→ horizontal asymptote: $y = 0$

2. Case 2:

if: degree of numerator = degree of denominator

then: horizontal asymptote: y = $\frac{leading\; coefficient \;of\; numerator}{leading\; coefficient\; of\; denominator}$

$i.e. f(x) = \frac{ax^{5}+......}{bx^{5}+......}$→ horizontal asymptote: $y = \frac{a}{b}$

3. Case 3:

if: degree of numerator > degree of denominator

then: horizontal asymptote: NONE

$i.e. f(x) = \frac{ax^{5}+......}{bx^{3}+......}$$NO\; horizontal\; asymptote$

2. Graphing Rational Functions

Sketch each rational function by determining:

i) vertical asymptote.

ii) horizontal asymptotes

1. $f\left( x \right) = \frac{5}{{2x + 10}}$
2. $g\left( x \right) = \frac{{5{x^2} - 13x + 6}}{{ - 2{x^2} + 3x + 2}}$
3. $h\left( x \right) = \frac{{{x^3}}}{{20x - 100}}$
3. Identifying Characteristics of Rational Functions

Without sketching the graph, determine the following features for each rational function:

i) point of discontinuity

ii) vertical asymptote

iii) horizontal asymptote

iv) slant asymptote

1. $a(x) = \frac{x - 9}{x + 9}$
2. $b(x) = \frac{x^{2}-9}{x^{2}+9}$
3. $c(x) = \frac{x^{2}+9}{x^{2}-9}$
4. $d(x) = \frac{x+9}{x^{2}-9}$
5. $e(x) = \frac{x+3}{x^{2}-9}$
6. $f(x) = \frac{x^{2}+9}{x+9}$
7. $g(x) = \frac{-x-9}{-x^{2}-9}$
8. $h(x) = \frac{-x^{2}-9}{-x^{2}+9}$
9. $i(x) = \frac{x^{2}-9}{x+3}$
10. $j(x) = \frac{x^{3}-9x^{2}}{x^{2}-3x}$
###### Topic Notes

There are 3 cases to consider when determining horizontal asymptotes:

1) Case 1:

if: degree of numerator < degree of denominator

then: horizontal asymptote: y = 0 (x-axis)

$i.e. f(x) = \frac{ax^{3}+......}{bx^{5}+......}$→ horizontal asymptote: $y = 0$

2) Case 2:

if: degree of numerator = degree of denominator

then: horizontal asymptote: y = $\frac{leading\; coefficient \;of\; numerator}{leading\; coefficient\; of\; denominator}$

$i.e. f(x) = \frac{ax^{5}+......}{bx^{5}+......}$→ horizontal asymptote: $y = \frac{a}{b}$

3) Case 3:

if: degree of numerator > degree of denominator

then: horizontal asymptote: NONE

$i.e. f(x) = \frac{ax^{5}+......}{bx^{3}+......}$$NO\; horizontal\; asymptote$