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Understanding polynomial functions, their graphs, and how to determine end behavior
Learn step-by-step with practice exercises built right in.
A polynomial function is a function that can be written in the form:
where:
The degree is the highest power of in the polynomial.
The leading coefficient is the coefficient of the term with the highest power.
Example:
End behavior describes what happens to as and .
The end behavior depends on:
| Degree | Leading Coefficient | Left End | Right End |
|---|---|---|---|
| Even | Positive (+) | ||
| Even | Negative (-) | ||
| Odd | Positive (+) | ||
| Odd | Negative (-) |
The zeros (or roots) of a polynomial are the values of where .
The multiplicity of a zero is how many times that factor appears.
To analyze a polynomial:
Determine the end behavior of .
Solution:
Step 1: Identify the degree and leading coefficient.
Step 2: Apply the end behavior rules.
Since the degree is odd and the leading coefficient is negative:
Consider the polynomial function .
Given , find all zeros and their multiplicities, then describe the graph behavior at each zero.
A polynomial function has the following properties:
Write a polynomial function with zeros at (multiplicity 2), (multiplicity 1), and (multiplicity 1), and end behavior where as .
Avoid these 4 frequent errors
See how this math is used in the real world
A stone is dropped into a still pond, creating a circular ripple. The radius of the ripple is increasing at a rate of cm/s. How fast is the area of the circle increasing when the radius is cm?
Answer:
a) What is the degree of this polynomial? b) What is the leading coefficient? c) Describe the end behavior of this function.
Solution:
Part (a): The degree is the highest power of in the polynomial.
The highest power is , so the degree is 5.
Part (b): The leading coefficient is the coefficient of the term with the highest power.
The coefficient of is , so the leading coefficient is -2.
Part (c): For end behavior, we look at the degree and leading coefficient:
For a polynomial with odd degree and negative leading coefficient:
In words: The graph rises to the left and falls to the right.
Solution:
Step 1: Find the zeros by setting each factor equal to zero.
Step 2: Determine the multiplicity of each zero.
Step 3: Describe behavior at each zero.
Step 4: Determine overall end behavior.
Answer: Zeros at (crosses), (touches), and (crosses)
a) Write a general form for using the known zeros. b) Find the specific equation for . c) Describe the end behavior.
Solution:
Part (a): With zeros at , the function has factors , , and .
Since the degree is 4 and we only have 3 zeros (each multiplicity 1), we need one more factor. Let's call it where is unknown.
General form:
where is a positive constant.
Part (b): We use the point to find and .
However, with two unknowns and one equation, we need more information. Let's assume the fourth zero is actually a repeated zero. If has multiplicity 2:
Substituting :
But we need positive! So let's try with multiplicity 2:
Therefore:
Part (c): Degree 4 (even), positive leading coefficient:
The graph rises on both ends.
Solution:
Step 1: Write the polynomial in factored form using the zeros.
With zeros at (mult. 2), (mult. 1), and (mult. 1):
Step 2: Determine the sign of the leading coefficient.
Total degree: (even)
For both ends to go to with an even degree, we need a negative leading coefficient.
So . We can choose .
Step 3: Verify (optional - expand to check).
If we expand:
The leading term will be , confirming our negative leading coefficient.
Answer: or any negative constant multiple