3. Rational Funcion
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Transcript of 3. Rational Funcion
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Rational Functionswith Homero Simpson
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1. Define rational functions. 2. Find the domain of a rational
function. 3. Find the asymptotes of a rational
function. 4. Draw the graph of a rational function.
Objectives
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AsymptoteOne way to study the behavior of a function when the values tend to infinity or at the points where the function is not defined (isolated points) is to compare the function with a straight line, so we say that a line is an asymptote of function when the graph of the function and the line remain very close. Depending on the line as we have three types of asymptotes: Vertical, Horizontal and Oblique.
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But what is the definition of a rational function? It is the function of the form
R x p xq x
( ) ( )( )
Where p (x) and q (x) are polynomial functions q (x) is not zero.
The domain consists of all real numbers except those for which the denominator q (x) is 0. Polynomial is the sum of several
monomials.
Monomial: algebraic expression in which letters, numbers and symbols are used
Domain: The set of values for which a function is defined
Codomain: One function is the set involved in that function.
YXf : Y
But it's function? It is the term used to
indicate the relationship or correspondence between
two or more quantities.
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Example: Find the domain of the following rational functions:
Real Numbers: include rational numbers (such as 31, 37) and to those Irrational numbers can not be expressed fractionally and have infinite decimal places.
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DefiniciónIf x tends to (x ) ó x -, and the value of R (x) to a fixed number L is about, then the line y = L is a horizontal asymptote of the graph of R.
y = L
y = R(x)
x
horizontal asymptote
Asymptote: A function whose graph representation is in the form of a straight
line or parabola and its trajectory is approaching a curve.
Horizontal Asymptote: It's called horizontal asymptote. The value (Real number) tends to F (x) to increase (or decrease) the x indefinitely.
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y = L
y = R(x)y
x
x
y = L
y = R(x)
y
x
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If x approaches a real number c, and the value of |R(x)| , “spproaches infinity ", then the line x = c is a vertical asymptote of the graph of R.
y
x
Vertical asymptote x = c
xVertical asymptotes: vertical lines are to which the function is approaching indefinitely without ever cutting.
Infinity: Any reference to an amount no limit or end, as opposed to the concept of finitude.
Finito: A group with a finite number of elements.
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definition
If an asymptote is neither horizontal nor vertical is called oblique asymptote.
y
x
Oblique asymptote
Oblique asymptotes are straight equation
nmxY xxfm )(lim
x
For values of x increasing (in absolute value), the points on the line and the graph of the function are increasingly coming.
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Theorem of Vertical Asymptotes
Asymptote: It tells a function f (x) to a straight t whose distance from the curve tends to zero when x tends to infinity or x tends to a point a.
A rational function in reduced form, has a vertical asymptote at x = r, si x –r is a factor of the denominator q(x); is, q(r )= 0 .
The line x=a is vertical asymptote (AV) de f(x) if limx->a+ f(x) = inf olimx->a- f(x) = inf.
EYE: To x = r is a vertical asymptote q(r) = 0 but p(r) ≠ 0.
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Example Find the vertical asymptotes of the graph of each rational function, if any.
2
3(a) ( )1
R xx
3( 1)( 1)x x
The graph has vertical asymptotes at : x = - 1 y en x = 1
2
3(b) ( )12
xR xx x
3( 3)( 4)
xx x
1
4x
The graph has a vertical asymptote at x = - 4
2
5(b) ( )1
xR xx
2 1 0x x i R
The graph has no vertical asymptotes
2
4(c) ( )12
xR xx x
4
( 3)( 4)x
x x
13x
The graph has a vertical asymptote has x = 3
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Theorem horizontal and oblique asymptotes - Consider the rational function
R x p xq x
a x a x a x ab x b x b x bn
nn
n
mm
mm( ) ( )
( )
11
1 0
11
1 0
1. If n < m, then the line y = 0 is an horizontal asymptote of the graph of R.
2. If n = m, then the line y = an / bm is an horizontal asymptote of the graph of R.
wherein the degree of the numerator is the degree of the denominator n is m.
http://www.coolmath.com/graphit/
The best way to have a reference of how to graph is
using
It is very easy to use
3. Ifi n = m + 1, then the line y = ax + b is an oblique asymptote of the graph of R, where ax + b is the quotient of the division between p (x) y q (x).
4. If n > m + 1, he graph of R is not linear or horizontal or oblique asymptotes.
Horizontal asymptotes: We tend to indicate the function when x is large or very small mus also are parallel to the axis OX lines. Written y= asymptotic value. Oblique Asymptotes: A rational function has oblique asymptote when the degree of the numerator is greater than the degree of the denominator unit.
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2
3 2
3 4 15(a) ( )4 7 1x xR x
x x x
The horizontal asymptote is: y = 0
2
2
2 4 1(b) ( )3 5x xR xx x
The horizontal asymptote is; y = 2/3
Example Find the horizontal or oblique asymptote of the graph of the function, if any.
The oblique asymptote is; y = x + 62 4 1(c) ( )
2x xR xx
2
2
6 2 4 1
- 2
6 1
- 6 12
13
xx x x
x x
xx
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QUESTIONS?
THANK YOU