Chapter 11: Problem 37
Graph each polynomial function. Factor first if the expression is not in factored form. Use the rational zeros theorem as necessary. \(f(x)=x^{2}(x-2)(x+3)^{2}\)
Short Answer
Expert verified
Zeros at \( x = 0 \), \( x = 2 \), and \( x = -3 \). The graph touches at \( x = 0 \) and \( x = -3 \), crosses at \( x = 2 \).
Step by step solution
01
Identify the Polynomial
The given polynomial is already in its factored form: \[ f(x) = x^{2}(x-2)(x+3)^{2} \] There is no need for further factoring.
02
Find the Zeros
Set each factor equal to zero and solve for x to find the zeros of the polynomial: \[ x^2 = 0 \rightarrow x = 0 \] \[ x - 2 = 0 \rightarrow x = 2 \] \[ (x + 3)^2 = 0 \rightarrow x = -3 \] Therefore, the zeros are \( x = 0, 2, -3 \).
03
Determine the Multiplicity of Each Zero
Examine the factors to determine the multiplicity of each zero: - The zero \( x = 0 \) has multiplicity 2 because \( x^2 \) appears in the polynomial. - The zero \( x = 2 \) has multiplicity 1 because \( x - 2 \) appears linearly. - The zero \( x = -3 \) has multiplicity 2 because \( (x + 3)^2 \) appears in the polynomial.
04
Analyze the Behavior at Each Zero
Zeros with even multiplicity (\( x = 0 \) and \( x = -3 \)) will touch and bounce off the x-axis. Zeros with odd multiplicity (\( x = 2 \)) will cross the x-axis.
05
Identify the End Behavior
Since the leading term of the polynomial when expanded is \( x^{5} \), the polynomial has odd degree, and the leading coefficient is positive. Therefore: - As \( x \rightarrow -\infty \), \( f(x) \rightarrow -\infty \). - As \( x \rightarrow +\infty \), \( f(x) \rightarrow +\infty \).
06
Sketch the Graph
Place the zeros \( 0, 2, -3 \) on the x-axis. From the end behavior, the graph will fall to the left and rise to the right. At \( x = 0 \), the graph will just touch the x-axis and bounce back up. At \( x = -3 \), the graph will touch the x-axis and bounce back down. At \( x = 2 \), the graph will cross the x-axis.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Factoring Polynomials
When solving a polynomial function, the first step is identifying if it is in its factored form. A polynomial is in factored form when it is expressed as the product of its factors. For example, the given polynomial is f(x) = x^2(x-2)(x+3)^2. Each part, like x^2, (x-2), and (x+3)^2, is a factor.Factoring helps in several ways:
- It simplifies the process of finding zeros.
- It reveals the polynomial's structure, making graphing easier.
Finding Zeros
The zeros of a polynomial are the values of x where the polynomial equals zero. They are crucial for graphing because they indicate where the graph intersects the x-axis. To find them:
- Set each factor in the polynomial equal to zero.
- Solve the equations.
In the exercise, we have: - From x^2 = 0, we get x = 0.
- From x - 2 = 0, we get x = 2.
- From (x + 3)^2 = 0, we get x = -3.
Multiplicity of Zeros
Multiplicity refers to the number of times a particular zero appears due to repeated factors. It influences the graph's behavior at these points:
- Even multiplicity: The graph touches the x-axis but bounces off instead of crossing it.
- Odd multiplicity: The graph crosses the x-axis.
- Zero x = 0 has a multiplicity of 2, due to the factor x^2.
- Zero x = 2 has a multiplicity of 1, because of the linear factor x - 2.
- Zero x = -3 has a multiplicity of 2, due to the factor (x + 3)^2.
End Behavior
End behavior describes how the polynomial function behaves as x approaches infinity or negative infinity. It's mainly determined by the polynomial's leading term. When expanded, the polynomial f(x) = x^2(x-2)(x+3)^2 becomes a fifth-degree polynomial (highest power is 5) with a positive leading coefficient.
Thus, its end behavior is:
Thus, its end behavior is:
- As x → -∞, f(x) → -∞.
- As x → +∞, f(x) → +∞.