Math worksheet for students to analyze and describe the graphs of polynomial functions, including identifying key features like degree, intercepts, and multiplicity.
Worksheet titled "Graph of a Polynomial Function" with two polynomial functions, their graphs, and questions about end behavior, degree, leading coefficient, turning points, intercepts, and multiplicity of zeros.
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Step-by-step solution for: Graph of a Polynomial Function worksheet
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Show Answer Key & Explanations
Step-by-step solution for: Graph of a Polynomial Function worksheet
Let's solve the two polynomial functions step by step based on the graph and the given equations. We'll analyze each function using key characteristics: end behavior, degree, sign of leading coefficient, number of turning points, intercepts, and multiplicity of zeros.
---
#### Step 1: Degree
The highest power of $ x $ is 5 → Degree = 5
#### Step 2: Sign of Leading Coefficient
The leading term is $ -x^5 $, so the leading coefficient is negative.
#### Step 3: End Behavior
- For odd degree (5) with negative leading coefficient:
- As $ x \to \infty $, $ f(x) \to -\infty $
- As $ x \to -\infty $, $ f(x) \to \infty $
- So, End behavior: Falls to the right, rises to the left.
#### Step 4: Number of Turning Points
A polynomial of degree $ n $ has at most $ n-1 $ turning points.
- Degree 5 → Max of $ 5-1 = 4 $ turning points.
- From the graph: There are 4 turning points (peaks and valleys).
#### Step 5: y-intercept
Set $ x = 0 $:
$$
f(0) = -(0)^5 + 2(0)^3 - 0 = 0
$$
→ $ y = 0 $
#### Step 6: x-intercepts
Solve $ f(x) = 0 $:
$$
f(x) = -x^5 + 2x^3 - x = -x(x^4 - 2x^2 + 1)
$$
Factor further:
$$
= -x(x^2 - 1)^2 = -x(x - 1)^2(x + 1)^2
$$
So, zeros are:
- $ x = 0 $
- $ x = 1 $ (multiplicity 2)
- $ x = -1 $ (multiplicity 2)
Thus, x-intercepts: $ x = -1, 0, 1 $
#### Step 7: Multiplicity of Zeros
From factored form: $ f(x) = -x(x - 1)^2(x + 1)^2 $
- At $ x = -1 $: multiplicity 2 → Graph touches and turns around (bounces)
- At $ x = 0 $: multiplicity 1 → Graph crosses the x-axis
- At $ x = 1 $: multiplicity 2 → Graph touches and turns around
Now fill in:
> The graph touches the x-axis at $ x = -1 $ → $ x = -1 $ has multiplicity 2
> The graph crosses the x-axis at $ x = 0 $ → $ x = 0 $ has multiplicity 1
> The graph touches the x-axis at $ x = 1 $ → $ x = 1 $ has multiplicity 2
---
| Feature | Answer |
|--------|--------|
| End behavior | Falls to the right, rises to the left |
| Degree | 5 |
| Sign of leading coefficient | Negative |
| No. of turning points | 4 |
| y-intercept | $ y = 0 $ |
| x-intercepts | $ x = -1, 0, 1 $ |
| Multiplicity | |
| - at $ x = -1 $: touches → mult. 2 | |
| - at $ x = 0 $: crosses → mult. 1 | |
| - at $ x = 1 $: touches → mult. 2 | |
---
#### Step 1: Degree
Highest power is 4 → Degree = 4
#### Step 2: Sign of Leading Coefficient
Leading term: $ x^4 $ → coefficient is positive
#### Step 3: End Behavior
Even degree (4), positive leading coefficient:
- As $ x \to \infty $, $ f(x) \to \infty $
- As $ x \to -\infty $, $ f(x) \to \infty $
→ End behavior: Rises to both ends
#### Step 4: Number of Turning Points
Max = $ 4 - 1 = 3 $
From the graph: There are 3 turning points
#### Step 5: y-intercept
Set $ x = 0 $:
$$
f(0) = 0 - 0 - 0 = 0
\Rightarrow y = 0
$$
#### Step 6: x-intercepts
Solve $ f(x) = 0 $:
$$
f(x) = x^4 - 3x^2 - 2x = x(x^3 - 3x - 2)
$$
Try rational roots for $ x^3 - 3x - 2 $. Try $ x = -1 $:
$$
(-1)^3 - 3(-1) - 2 = -1 + 3 - 2 = 0 → x = -1 \text{ is a root}
$$
Use synthetic division or factor:
$$
x^3 - 3x - 2 = (x + 1)(x^2 - x - 2)
$$
Factor quadratic:
$$
x^2 - x - 2 = (x - 2)(x + 1)
$$
So:
$$
f(x) = x(x + 1)(x - 2)(x + 1) = x(x + 1)^2(x - 2)
$$
Zeros:
- $ x = 0 $
- $ x = -1 $ (multiplicity 2)
- $ x = 2 $
So, x-intercepts: $ x = -1, 0, 2 $
#### Step 7: Multiplicity of Zeros
From $ f(x) = x(x + 1)^2(x - 2) $
- $ x = -1 $: multiplicity 2 → graph touches and turns
- $ x = 0 $: multiplicity 1 → graph crosses
- $ x = 2 $: multiplicity 1 → graph crosses
Now fill in:
> The graph touches the x-axis at $ x = -1 $ → $ x = -1 $ has multiplicity 2
> The graph crosses the x-axis at $ x = 0 $ → $ x = 0 $ has multiplicity 1
> The graph crosses the x-axis at $ x = 2 $ → $ x = 2 $ has multiplicity 1
---
| Feature | Answer |
|--------|--------|
| End behavior | Rises to both ends |
| Degree | 4 |
| Sign of leading coefficient | Positive |
| No. of turning points | 3 |
| y-intercept | $ y = 0 $ |
| x-intercepts | $ x = -1, 0, 2 $ |
| Multiplicity | |
| - at $ x = -1 $: touches → mult. 2 | |
| - at $ x = 0 $: crosses → mult. 1 | |
| - at $ x = 2 $: crosses → mult. 1 | |
---
---
- End behavior of the graph → Falls to the right, rises to the left
- Degree → 5
- Sign of the leading coefficient → Negative
- No. of turning points → 4
- y-intercept → $ y = 0 $
- x-intercepts → $ x = -1, 0, 1 $
- Multiplicity of zeros:
- The graph touches the x-axis at $ x = -1 $ → $ x = -1 $ has multiplicity 2
- The graph crosses the x-axis at $ x = 0 $ → $ x = 0 $ has multiplicity 1
- The graph touches the x-axis at $ x = 1 $ → $ x = 1 $ has multiplicity 2
---
- End behavior of the graph → Rises to both ends
- Degree → 4
- Sign of the leading coefficient → Positive
- No. of turning points → 3
- y-intercept → $ y = 0 $
- x-intercepts → $ x = -1, 0, 2 $
- Multiplicity of zeros:
- The graph touches the x-axis at $ x = -1 $ → $ x = -1 $ has multiplicity 2
- The graph crosses the x-axis at $ x = 0 $ → $ x = 0 $ has multiplicity 1
- The graph crosses the x-axis at $ x = 2 $ → $ x = 2 $ has multiplicity 1
---
✔ How many attempts? (You can write "1" if you did it correctly first time)
✔ How well did you do? Choose: 😂 Need help! 😊 Just OK! 😄 Splendid
You can now confidently fill in the worksheet!
Let me know if you want this formatted as a printable answer sheet!
---
Problem 1: $ f(x) = -x^5 + 2x^3 - x $
#### Step 1: Degree
The highest power of $ x $ is 5 → Degree = 5
#### Step 2: Sign of Leading Coefficient
The leading term is $ -x^5 $, so the leading coefficient is negative.
#### Step 3: End Behavior
- For odd degree (5) with negative leading coefficient:
- As $ x \to \infty $, $ f(x) \to -\infty $
- As $ x \to -\infty $, $ f(x) \to \infty $
- So, End behavior: Falls to the right, rises to the left.
#### Step 4: Number of Turning Points
A polynomial of degree $ n $ has at most $ n-1 $ turning points.
- Degree 5 → Max of $ 5-1 = 4 $ turning points.
- From the graph: There are 4 turning points (peaks and valleys).
#### Step 5: y-intercept
Set $ x = 0 $:
$$
f(0) = -(0)^5 + 2(0)^3 - 0 = 0
$$
→ $ y = 0 $
#### Step 6: x-intercepts
Solve $ f(x) = 0 $:
$$
f(x) = -x^5 + 2x^3 - x = -x(x^4 - 2x^2 + 1)
$$
Factor further:
$$
= -x(x^2 - 1)^2 = -x(x - 1)^2(x + 1)^2
$$
So, zeros are:
- $ x = 0 $
- $ x = 1 $ (multiplicity 2)
- $ x = -1 $ (multiplicity 2)
Thus, x-intercepts: $ x = -1, 0, 1 $
#### Step 7: Multiplicity of Zeros
From factored form: $ f(x) = -x(x - 1)^2(x + 1)^2 $
- At $ x = -1 $: multiplicity 2 → Graph touches and turns around (bounces)
- At $ x = 0 $: multiplicity 1 → Graph crosses the x-axis
- At $ x = 1 $: multiplicity 2 → Graph touches and turns around
Now fill in:
> The graph touches the x-axis at $ x = -1 $ → $ x = -1 $ has multiplicity 2
> The graph crosses the x-axis at $ x = 0 $ → $ x = 0 $ has multiplicity 1
> The graph touches the x-axis at $ x = 1 $ → $ x = 1 $ has multiplicity 2
---
✔ Summary for Problem 1:
| Feature | Answer |
|--------|--------|
| End behavior | Falls to the right, rises to the left |
| Degree | 5 |
| Sign of leading coefficient | Negative |
| No. of turning points | 4 |
| y-intercept | $ y = 0 $ |
| x-intercepts | $ x = -1, 0, 1 $ |
| Multiplicity | |
| - at $ x = -1 $: touches → mult. 2 | |
| - at $ x = 0 $: crosses → mult. 1 | |
| - at $ x = 1 $: touches → mult. 2 | |
---
Problem 2: $ f(x) = x^4 - 3x^2 - 2x $
#### Step 1: Degree
Highest power is 4 → Degree = 4
#### Step 2: Sign of Leading Coefficient
Leading term: $ x^4 $ → coefficient is positive
#### Step 3: End Behavior
Even degree (4), positive leading coefficient:
- As $ x \to \infty $, $ f(x) \to \infty $
- As $ x \to -\infty $, $ f(x) \to \infty $
→ End behavior: Rises to both ends
#### Step 4: Number of Turning Points
Max = $ 4 - 1 = 3 $
From the graph: There are 3 turning points
#### Step 5: y-intercept
Set $ x = 0 $:
$$
f(0) = 0 - 0 - 0 = 0
\Rightarrow y = 0
$$
#### Step 6: x-intercepts
Solve $ f(x) = 0 $:
$$
f(x) = x^4 - 3x^2 - 2x = x(x^3 - 3x - 2)
$$
Try rational roots for $ x^3 - 3x - 2 $. Try $ x = -1 $:
$$
(-1)^3 - 3(-1) - 2 = -1 + 3 - 2 = 0 → x = -1 \text{ is a root}
$$
Use synthetic division or factor:
$$
x^3 - 3x - 2 = (x + 1)(x^2 - x - 2)
$$
Factor quadratic:
$$
x^2 - x - 2 = (x - 2)(x + 1)
$$
So:
$$
f(x) = x(x + 1)(x - 2)(x + 1) = x(x + 1)^2(x - 2)
$$
Zeros:
- $ x = 0 $
- $ x = -1 $ (multiplicity 2)
- $ x = 2 $
So, x-intercepts: $ x = -1, 0, 2 $
#### Step 7: Multiplicity of Zeros
From $ f(x) = x(x + 1)^2(x - 2) $
- $ x = -1 $: multiplicity 2 → graph touches and turns
- $ x = 0 $: multiplicity 1 → graph crosses
- $ x = 2 $: multiplicity 1 → graph crosses
Now fill in:
> The graph touches the x-axis at $ x = -1 $ → $ x = -1 $ has multiplicity 2
> The graph crosses the x-axis at $ x = 0 $ → $ x = 0 $ has multiplicity 1
> The graph crosses the x-axis at $ x = 2 $ → $ x = 2 $ has multiplicity 1
---
✔ Summary for Problem 2:
| Feature | Answer |
|--------|--------|
| End behavior | Rises to both ends |
| Degree | 4 |
| Sign of leading coefficient | Positive |
| No. of turning points | 3 |
| y-intercept | $ y = 0 $ |
| x-intercepts | $ x = -1, 0, 2 $ |
| Multiplicity | |
| - at $ x = -1 $: touches → mult. 2 | |
| - at $ x = 0 $: crosses → mult. 1 | |
| - at $ x = 2 $: crosses → mult. 1 | |
---
Final Answers Filled In:
---
1. $ f(x) = -x^5 + 2x^3 - x $
- End behavior of the graph → Falls to the right, rises to the left
- Degree → 5
- Sign of the leading coefficient → Negative
- No. of turning points → 4
- y-intercept → $ y = 0 $
- x-intercepts → $ x = -1, 0, 1 $
- Multiplicity of zeros:
- The graph touches the x-axis at $ x = -1 $ → $ x = -1 $ has multiplicity 2
- The graph crosses the x-axis at $ x = 0 $ → $ x = 0 $ has multiplicity 1
- The graph touches the x-axis at $ x = 1 $ → $ x = 1 $ has multiplicity 2
---
2. $ f(x) = x^4 - 3x^2 - 2x $
- End behavior of the graph → Rises to both ends
- Degree → 4
- Sign of the leading coefficient → Positive
- No. of turning points → 3
- y-intercept → $ y = 0 $
- x-intercepts → $ x = -1, 0, 2 $
- Multiplicity of zeros:
- The graph touches the x-axis at $ x = -1 $ → $ x = -1 $ has multiplicity 2
- The graph crosses the x-axis at $ x = 0 $ → $ x = 0 $ has multiplicity 1
- The graph crosses the x-axis at $ x = 2 $ → $ x = 2 $ has multiplicity 1
---
✔ How many attempts? (You can write "1" if you did it correctly first time)
✔ How well did you do? Choose: 😂 Need help! 😊 Just OK! 😄 Splendid
You can now confidently fill in the worksheet!
Let me know if you want this formatted as a printable answer sheet!
Parent Tip: Review the logic above to help your child master the concept of polynomial function worksheet.