Chapter 4: Problem 76
Find only the rational zeros of the function. If there are none, state this. $$f(x)=x^{3}-x^{2}-4 x+3$$
Short Answer
Expert verified
There are no rational zeros.
Step by step solution
01
- State the Rational Root Theorem
The Rational Root Theorem states that any rational zero of a polynomial function, when written in the form of \ \(\frac{p}{q} \), is such that p is a factor of the constant term and q is a factor of the leading coefficient.
02
- Identify p and q
For the polynomial function \(f(x)=x^{3}-x^{2}-4x+3\), the constant term is 3 and the leading coefficient is 1. Therefore, p is a factor of 3 (\(\pm 1, \pm 3\)) and q is a factor of 1 (\(\pm 1\)).
03
- List all possible rational zeros
Using the factors of p and q, the possible rational zeros are \(\pm 1, \pm 3\).
04
- Test the possible rational zeros
Substitute each possible rational zero into the function \(f(x)\) to see if it equals 0:1. For \(x = 1\): \(f(1) = 1^{3} - 1^{2} - 4 (1) + 3 = 1 - 1 - 4 + 3 = -1\) (not a zero)2. For \(x = -1\): \(f(-1) = (-1)^{3} - (-1)^{2} - 4 (-1) + 3 = -1 - 1 + 4 + 3 = 5\) (not a zero)3. For \(x = 3\): \(f(3) = 3^{3} - 3^{2} - 4 (3) + 3 = 27 - 9 - 12 + 3 = 9\) (not a zero)4. For \ x = -3\: \(f(-3) = (-3)^{3} - (-3)^{2} - 4 (-3) + 3 = -27 - 9 + 12 + 3 = -21\) (not a zero)
05
- Conclude the result
Based on testing all the possible rational zeros, none of them resulted in \(f(x) = 0\). Hence, there are no rational zeros for the polynomial function \(f(x) = x^{3}-x^{2}-4x+3\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Polynomial Function
A polynomial function is a mathematical expression that consists of variables raised to whole number exponents and coefficients. For example, in the polynomial function \(f(x)=x^{3}-x^{2}-4x+3\), we have terms like \(x^{3}\), \(-x^{2}\), \(-4x\), and \(3\).
- The highest exponent, known as the degree of the polynomial, is three for this function.
- Each term has a coefficient, which multiplies the variable.
- The constant term is \(3\), which does not have a variable.
Rational Zeros
Rational zeros are the values of \(x\) for which the polynomial function equals zero and can be expressed as a fraction \(\frac{p}{q}\) where \(p\) and \(q\) are integers.The Rational Root Theorem helps in efficiently finding possible rational zeros of a polynomial.It states that if a polynomial has a rational zero, \(\frac{p}{q}\): `p` is a factor of the constant term. `q` is a factor of the leading coefficient. For the polynomial \(f(x)=x^{3}-x^{2}-4x+3\):
- The constant term is \(3\), so `p` can be \(\text{±1, ±3}\).
- The leading coefficient is \(1\), so `q` can be \(\text{±1}\).
Testing Possible Zeros
Testing each possible rational zero involves substituting them into the function and checking if the result equals zero.Let's apply this to our polynomial \(f(x)=x^{3}-x^{2}-4x+3\) by testing \(\text{±1}\) and \(\text{±3}\):
- For \(x=1\): \(f(1)=1^{3}-1^{2}-4(1)+3 = -1\) (not a zero)
- For \(x=-1\): \(f(-1)=(-1)^{3}-(-1)^{2}-4(-1)+3=5\) (not a zero)
- For \(x=3\): \(f(3)=3^{3}-3^{2}-4(3)+3=9\) (not a zero)
- For \(x=-3\): \(f(-3)=(-3)^{3}-(-3)^{2}-4(-3)+3=-21\) (not a zero)