Chapter 5: Problem 66
For the following exercises, use the given information about the polynomial graph to write the equation. Double zero at \(x=-3\) and triple zero at \(x=0\) . Passes through the point \((1,32)\) .
Short Answer
Expert verified
The polynomial is \(f(x) = 2(x + 3)^2 x^3\).
Step by step solution
01
Identify the Zeros and Multiplicities
We are given that the polynomial has a double zero at \(x = -3\) and a triple zero at \(x = 0\). This means the factors of the polynomial include \((x + 3)^2\) and \(x^3\). The general form of the polynomial is then \(f(x) = a \cdot (x + 3)^2 \cdot x^3\), where \(a\) is a constant we need to determine.
02
Substitute the Point into the Polynomial
We know that the polynomial passes through the point \((1,32)\). Substitute \(x = 1\) and \(f(x) = 32\) into the polynomial equation: \[ f(x) = a \cdot (x + 3)^2 \cdot x^3 \Rightarrow 32 = a \cdot (1 + 3)^2 \cdot 1^3. \]
03
Solve for the Constant 'a'
Simplify the equation from step 2: \[ 32 = a \cdot (4)^2 \cdot 1. \] This simplifies to \(32 = 16a\). Solve for \(a\) by dividing both sides of the equation by 16:\[ a = \frac{32}{16} = 2. \]
04
Write the Polynomial Equation
Now that we have found \(a = 2\), substitute it back into the general polynomial equation to get the specific equation: \[ f(x) = 2 \cdot (x + 3)^2 \cdot x^3. \] Simplify this to \[ f(x) = 2x^3(x^2 + 6x + 9). \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Zeros in Polynomials
Zeros of a polynomial are values of the variable that make the polynomial equal to zero. In simpler terms, zeros are the x-values where the graph of the polynomial intersects the x-axis. They are crucial because they tell us where the polynomial "dips" below the x-axis, hits it, or just touches it lightly.
- If a polynomial has a single zero, the graph crosses the x-axis at that point.
- A double zero means the graph touches the x-axis and turns back.
- A triple zero would cause the graph to flatten out at the axis before crossing.
The Role of Multiplicities
Multiplicities refer to the number of times a particular zero occurs in the polynomial. The multiplicity influences the shape and the behavior of the graph at that zero.
- A zero with odd multiplicity means the graph will pass through the x-axis at that zero.
- A zero with even multiplicity causes the graph to just touch the x-axis and turn back.
Factored Form and Its Benefits
Writing a polynomial in its factored form means expressing it as a product of its zero-determined factors. This method is beneficial for easily identifying zeros and their multiplicities. The process converts the polynomial into a form that highlights its root characteristics.
- In our exercise, the factors are \((x+3)^2\) and \(x^3\), showing the zeros at \(x=-3\) and \(x=0\) respectively.
- The exponents on these factors (2 and 3) show the multiplicities of the corresponding zeros.
Finding Polynomial Equations from Graph Information
To find a polynomial equation from graph information, you need zeros, their multiplicities, and potentially a point that the graph passes through. Here are the key steps:
- Identify the zeros and set up the factors with their respective multiplicities. For example, a double zero at \(x=-3\) becomes \((x+3)^2\).
- Include a variable constant \(a\) which is solved using the given point that the graph passes through.
- Substitute the x-value of this point into your equation and solve for \(a\), ensuring the equation matches the point's y-value.