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AP Precalculus
Unit 1: Polynomial and Rational Functions
1.2 Describing end behavior of polynomial and rational functions
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Steps to determine the end behavior of a polynomial function
1️⃣ Identify the degree of the polynomial
2️⃣ Identify the leading coefficient
3️⃣ Use the degree and leading coefficient to describe the end behavior
Match the degree and leading coefficient with the correct end behavior:
Even degree, Negative leading coefficient ↔️ Both ends approach -∞
Odd degree, Negative leading coefficient ↔️ Left: ∞, Right: -∞
What is the degree and leading coefficient of
3
x
4
−
5
x
2
+
3x^{4} - 5x^{2} +
3
x
4
−
5
x
2
+
2
x
−
7
2x - 7
2
x
−
7
?
Degree: 4, Coefficient: 3
What determines the end behavior of a rational function?
Horizontal asymptotes
The end behavior of a rational function is determined by the presence of horizontal
asymptotes
When the degree of the numerator is greater than the degree of the denominator, there is no
horizontal asymptote
.
True
If the degree of a polynomial is even and the leading coefficient is positive, both ends approach positive
infinity
The degree of a polynomial is the highest power of
x
Describe the end behavior of the polynomial
f
(
x
)
=
f(x) =
f
(
x
)
=
2
x
3
−
5
x
+
2x^{3} - 5x +
2
x
3
−
5
x
+
1
1
1
.
f
(
x
)
→
−
∞
f(x) \to - \infty
f
(
x
)
→
−
∞
as
x
→
−
∞
x \to - \infty
x
→
−
∞
and
f
(
x
)
→
∞
f(x) \to \infty
f
(
x
)
→
∞
as
x
→
∞
x \to \infty
x
→
∞
For
f
(
x
)
=
f(x) =
f
(
x
)
=
\frac{3x^{2} +
1}{x^{2} - 4}
, the horizontal asymptote is 3
The degree of the denominator in a rational function is the highest power of
x
Match the degree and leading coefficient with the correct end behavior:
Even, Positive ↔️
f
(
x
)
→
∞
f(x) \to \infty
f
(
x
)
→
∞
as
x
→
±
∞
x \to \pm \infty
x
→
±
∞
Even, Negative ↔️
f
(
x
)
→
−
∞
f(x) \to - \infty
f
(
x
)
→
−
∞
as
x
→
±
∞
x \to \pm \infty
x
→
±
∞
Odd, Positive ↔️
f
(
x
)
→
−
∞
f(x) \to - \infty
f
(
x
)
→
−
∞
as
x
→
−
∞
x \to - \infty
x
→
−
∞
and
f
(
x
)
→
∞
f(x) \to \infty
f
(
x
)
→
∞
as
x
→
∞
x \to \infty
x
→
∞
Odd, Negative ↔️
f
(
x
)
→
∞
f(x) \to \infty
f
(
x
)
→
∞
as
x
→
−
∞
x \to - \infty
x
→
−
∞
and
f
(
x
)
→
−
∞
f(x) \to - \infty
f
(
x
)
→
−
∞
as
x
→
∞
x \to \infty
x
→
∞
For the polynomial f(x) = 2x^{3} - 5x + 1</latex>, what is its degree?
3
What is the horizontal asymptote when the degree of the numerator is less than the degree of the denominator?
y
=
y =
y
=
0
0
0
If the degree of the numerator is less than the degree of the denominator, the horizontal asymptote is
y
=
y =
y
=
0
0
0
.
True
For
f
(
x
)
=
f(x) =
f
(
x
)
=
\frac{3x^{2} +
1}{x^{2} - 4}
, the horizontal asymptote is
y
=
y =
y
=
3
3
3
.
True
What is the degree of the numerator in a rational function?
Highest power of
x
x
x
For polynomial functions, the end behavior depends on the degree and the
leading
coefficient.
What is the end behavior of
f
(
x
)
=
f(x) =
f
(
x
)
=
3
x
4
−
2
x
+
3x^{4} - 2x +
3
x
4
−
2
x
+
1
1
1
?
f
(
x
)
→
∞
f(x) \to \infty
f
(
x
)
→
∞
as
x
→
±
∞
x \to \pm \infty
x
→
±
∞
What happens to the end behavior of a rational function if the degree of the numerator is greater than the denominator?
f
(
x
)
f(x)
f
(
x
)
increases or decreases without bound
The end behavior of a polynomial function is determined by the leading coefficient and the
degree
What is the end behavior of a polynomial with an odd degree and a positive leading coefficient?
Left: -∞, Right: ∞
The leading coefficient is the coefficient in front of the term with the highest power of
x
A polynomial with an odd degree and a negative leading coefficient approaches positive infinity on the left and negative infinity on the right.
True
What does the end behavior of a rational function describe?
Behavior as
x
→
±
∞
x \to \pm \infty
x
→
±
∞
What is the horizontal asymptote when the degrees of the numerator and denominator are equal?
y
=
y =
y
=
leading coefficient of numerator
leading coefficient of denominator
\frac{\text{leading coefficient of numerator}}{\text{leading coefficient of denominator}}
leading coefficient of denominator
leading coefficient of numerator
What determines the end behavior of a polynomial function?
Degree and leading coefficient
Match the degree and leading coefficient with the corresponding end behavior:
Even degree, positive leading coefficient ↔️
f
(
x
)
→
∞
f(x) \to \infty
f
(
x
)
→
∞
as
x
→
±
∞
x \to \pm \infty
x
→
±
∞
Even degree, negative leading coefficient ↔️
f
(
x
)
→
−
∞
f(x) \to - \infty
f
(
x
)
→
−
∞
as
x
→
±
∞
x \to \pm \infty
x
→
±
∞
Odd degree, positive leading coefficient ↔️
f
(
x
)
→
−
∞
f(x) \to - \infty
f
(
x
)
→
−
∞
as
x
→
−
∞
x \to - \infty
x
→
−
∞
and
f
(
x
)
→
∞
f(x) \to \infty
f
(
x
)
→
∞
as
x
→
∞
x \to \infty
x
→
∞
For the polynomial
3
x
4
−
5
x
2
+
3x^{4} - 5x^{2} +
3
x
4
−
5
x
2
+
2
x
−
7
2x - 7
2
x
−
7
, the degree is
4
4
4
and the leading coefficient is
3
3
3
.
True
Identifying the degrees of the numerator and denominator is crucial for determining the end behavior of
rational functions
.
True
What is the degree of the numerator in a rational function?
The highest power of x
What is the end behavior of an even degree polynomial with a positive leading coefficient?
f
(
x
)
→
∞
f(x) \to \infty
f
(
x
)
→
∞
as
x
→
±
∞
x \to \pm \infty
x
→
±
∞
The leading coefficient is the coefficient of the term with the highest power of
x
x
x
.
True
Match the degree comparison with the correct end behavior of rational functions:
Numerator < Denominator ↔️
f
(
x
)
→
0
f(x) \to 0
f
(
x
)
→
0
as
x
→
±
∞
x \to \pm \infty
x
→
±
∞
Numerator = Denominator ↔️
f
(
x
)
→
y
f(x) \to y
f
(
x
)
→
y
as
x
→
±
∞
x \to \pm \infty
x
→
±
∞
Numerator > Denominator ↔️
f
(
x
)
→
∞
f(x) \to \infty
f
(
x
)
→
∞
or
f
(
x
)
→
−
∞
f(x) \to - \infty
f
(
x
)
→
−
∞
as
x
→
±
∞
x \to \pm \infty
x
→
±
∞
What guides the end behavior of rational functions?
Horizontal asymptotes
What happens to the end behavior of a rational function if the degree of the numerator is greater than the degree of the denominator?
f
(
x
)
→
∞
f(x) \to \infty
f
(
x
)
→
∞
or
f
(
x
)
→
−
∞
f(x) \to - \infty
f
(
x
)
→
−
∞
Match the degree comparison with the correct horizontal asymptote and end behavior:
Numerator < Denominator ↔️
y
=
y =
y
=
0
0
0
and
f
(
x
)
→
0
f(x) \to 0
f
(
x
)
→
0
Numerator = Denominator ↔️
y
=
y =
y
=
leading coefficient of numerator
leading coefficient of denominator
\frac{\text{leading coefficient of numerator}}{\text{leading coefficient of denominator}}
leading coefficient of denominator
leading coefficient of numerator
and
f
(
x
)
→
y
f(x) \to y
f
(
x
)
→
y
Numerator > Denominator ↔️ None and
f
(
x
)
→
∞
f(x) \to \infty
f
(
x
)
→
∞
or
f
(
x
)
→
−
∞
f(x) \to - \infty
f
(
x
)
→
−
∞
If the degree of the numerator is less than the denominator, what is the horizontal asymptote?
y
=
y =
y
=
0
0
0
If the degree of the numerator is less than the degree of the denominator, the end behavior is
f
(
x
)
→
0
f(x) \to 0
f
(
x
)
→
0
as
x
→
±
∞
x \to \pm \infty
x
→
±
∞
.
True
What does the end behavior of a polynomial function describe?
Function's behavior at infinity
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