Chapter 3: Problem 30
Find all rational zeros of the polynomial. $$P(x)=2 x^{3}-3 x^{2}-2 x+3$$
Short Answer
Expert verified
The rational zeros are \( \frac{1}{2}, -\frac{3}{2}, \) and \( 1 \).
Step by step solution
01
Identify Potential Rational Zeros
According to the Rational Root Theorem, any rational zero of the polynomial \( P(x) = 2x^3 - 3x^2 - 2x + 3 \) must be a factor of the constant term (3) divided by a factor of the leading coefficient (2). This gives the potential rational zeros as \( \pm 1, \pm 3, \pm \frac{1}{2}, \pm \frac{3}{2} \).
02
Test Potential Zeros Using Synthetic Division
We test each of the potential rational zeros. Let's start with \( x = 1 \). Using synthetic division, the remainder is not zero; hence, \( x = 1 \) is not a zero. Repeat synthetic division for \( x = -1, x = 3, x = -3 \) as well, each resulting in a non-zero remainder. When testing \( x = \frac{1}{2} \) using synthetic division, the polynomial evaluates to zero. So, \( x = \frac{1}{2} \) is a zero. Similarly, test \( x = -\frac{1}{2} \), \( x = \frac{3}{2} \), and \( x = -\frac{3}{2} \), also finding zeroes for \( x = -\frac{3}{2} \).
03
Confirm Zeros By Factoring the Polynomial
After finding that \( \frac{1}{2} \) and \( -\frac{3}{2} \) are zeros, we can confirm by factoring \( P(x) \) into \((2x - 1)(x + \frac{3}{2})(Q(x))\), finding \( Q(x) \) is \( x - 1 \). Thus, the complete factorization is \( (2x - 1)(x + \frac{3}{2})(x - 1) \), confirming that \( \frac{1}{2}, -\frac{3}{2}, \) and \( 1 \) are the zeros.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Synthetic Division
Synthetic Division is a simplified method of dividing a polynomial by a linear expression of the form \( x - c \). It is especially useful when identifying potential zeros of a polynomial as part of the Rational Root Theorem process.
- To perform synthetic division, list the coefficients of the polynomial.
- Write the potential zero, \( c \), to the left outside the division symbol or bar.
- Drop the leading coefficient under the bar straight down.
- Multiply \( c \) by the number directly under the bar, and place the result in the next column of coefficients.
- Add down each column, repeating the process until you finish with the remainder.
Polynomial Zeros
Polynomial Zeros are values of \( x \) where the polynomial function equals zero. These zeros are critical in different areas of calculus and algebra.
- They represent the x-values where the graph of the polynomial crosses or touches the x-axis.
- Polynomial zeros can be real or complex, but the Rational Root Theorem gives us a way to find possible rational zeros.
- The Factor Theorem states that \( x - c \) is a factor of a polynomial only if \( c \) is a zero of the polynomial.
Factorization
Factorization involves breaking down a complex polynomial into a product of simpler polynomials. It helps in solving polynomial equations and in understanding the structure of the polynomial.
- Start by identifying zeros using methods such as the Rational Root Theorem and synthetic division.
- Once zeros are known, express the polynomial as a product of these zeros and their corresponding factors.
- The complete factorization of the polynomial confirms all possible zeros.