Chapter 4: Problem 11
Find a polynomial function of degree 3 with the given numbers as zeros. $$-\frac{1}{3}, 0,2$$
Short Answer
Expert verified
y = 3x^3 - 5x^2 - 2x
Step by step solution
01
Write the Zeros as Factors
The polynomial function of degree 3 will be in the form of y = k(x - r_1)(x - r_2)(x - r_3),where k is a constant, and r_1, r_2, and r_3 are the given zeros. For the zeros $$-\frac{1}{3}, 0, 2$$, we have y = k(x + \frac{1}{3})(x)(x - 2).
02
Simplify the Factors
Since having a fractional zero can make the polynomial less clear, multiply the factor $$\frac{1}{3}$$ by 3, to get integer coefficients. Therefore,y = k(3x + 1)(x)(x - 2).
03
Multiple the Factors
First, multiply the factors (x) and (3x + 1):y = k [(x)(3x + 1)](x - 2)y = k (3x^2 + x)(x - 2).
04
Expand the Polynomial
Next, distribute the (3x^2 + x) term over the (x - 2) term:y = k [(3x^2 + x)(x - 2)]y = k (3x^3 - 6x^2 + x^2 - 2x)y = k (3x^3 - 5x^2 -2x).
05
Determine the Leading Coefficient
Since the problem doesn't specify a leading coefficient, we can choose k = 1 for simplicity. Therefore, the final polynomial isy = 3x^3 - 5x^2 - 2x.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Degree of a Polynomial
In a polynomial function, the degree is the highest power of the variable, typically denoted as x. For example, in the polynomial \(3x^3 - 5x^2 - 2x\), the highest power of x is 3, which means this is a polynomial of degree 3. Understanding the degree of a polynomial helps us to determine the shape of its graph and the possible number of zeros it can have. A polynomial of degree n can have at most n real zeros.
Zeros of a Polynomial
Zeros of a polynomial (or roots) are the values of x that make the polynomial equal to zero. For example, if we have a polynomial with zeros at \(-\frac{1}{3}\), 0, and 2, it means that these values when substituted for x will make the polynomial zero. Zeros play a crucial role in factoring and graphing polynomials. To find the polynomial when zeros are given, we convert them into factors. Thus, zeros at \(-\frac{1}{3}\), 0, and 2 correspond to factors of \((x + \frac{1}{3})\), (x), and \((x - 2)\) respectively.
Factoring Polynomials
Factoring a polynomial involves writing it as a product of its factors. When given the zeros of a polynomial, like \(-\frac{1}{3}\), 0, and 2, we can turn these into factors. For simplicity, we often adjust factors to avoid fractions. For example, the factor corresponding to \(-\frac{1}{3}\) can be multiplied by 3, resulting in \(3x + 1\). The polynomial can then be expressed as a product of these factors: \((3x + 1)(x)(x - 2)\). This process simplifies solving and graphing the polynomial.
Polynomial Expansion
Polynomial expansion involves multiplying the factors to get the polynomial in standard form. For example, to expand \(y = (3x + 1)(x)(x - 2)\), we start by multiplying two of the factors: \((3x + 1)(x) = 3x^2 + x\). Next, we distribute this result over the third factor: \[ (3x^2 + x)(x - 2) = 3x^3 - 6x^2 + x^2 - 2x = 3x^3 - 5x^2 - 2x\].\ Note how each term is multiplied systematically. The final expanded polynomial is \(3x^3 - 5x^2 - 2x\), which is in standard form and ready for further analysis such as graphing or finding more properties.