Math Problem Statement

Use the Rational Zero Test to list the possible rational zeros of f. Verify that the zeros of f shown on the graph are contained in the list. (Enter your answers as a comma-separated list.) f(x) = 2x4 − 21x3 + 49x2 + 9x − 63

The x y-coordinate plane is given. The curve enters the window in the second quadrant, goes down and right becoming less steep, crosses the x-axis at x = −1, changes direction at the approximate point (−0.1, −63), goes up and right becoming more steep, crosses the y-axis at y = −63, passes through the approximate point (0.9, −27), goes up and right becoming less steep, crosses the x-axis at x = 1.5, changes direction at the approximate point (2.3, 17), goes down and right becoming more steep, crosses the x-axis at x = 3, and exits the window in the fourth quadrant. x =

Solution

To solve this problem, we'll use the Rational Zero Test (also known as the Rational Root Theorem) to list the possible rational zeros for the polynomial function:

f(x)=2x421x3+49x2+9x63f(x) = 2x^4 - 21x^3 + 49x^2 + 9x - 63

Step 1: The Rational Zero Test

The Rational Zero Test states that any rational zero of a polynomial function must be of the form:

pq\frac{p}{q}

Where:

  • pp is a factor of the constant term (the term without xx, which is 63-63).
  • qq is a factor of the leading coefficient (the coefficient of the highest degree term, which is 22).

Step 2: Identify factors of the constant term and leading coefficient

  • The constant term is 63-63, and its factors are: p=±1,±3,±7,±9,±21,±63p = \pm 1, \pm 3, \pm 7, \pm 9, \pm 21, \pm 63
  • The leading coefficient is 22, and its factors are: q=±1,±2q = \pm 1, \pm 2

Step 3: List all possible rational zeros

To list all possible rational zeros, we'll take all combinations of the factors of pp divided by the factors of qq:

pq=±11,±31,±71,±91,±211,±631,±12,±32,±72,±92,±212,±632\frac{p}{q} = \pm \frac{1}{1}, \pm \frac{3}{1}, \pm \frac{7}{1}, \pm \frac{9}{1}, \pm \frac{21}{1}, \pm \frac{63}{1}, \pm \frac{1}{2}, \pm \frac{3}{2}, \pm \frac{7}{2}, \pm \frac{9}{2}, \pm \frac{21}{2}, \pm \frac{63}{2}

Thus, the possible rational zeros are:

±1,±3,±7,±9,±21,±63,±12,±32,±72,±92,±212,±632\pm 1, \pm 3, \pm 7, \pm 9, \pm 21, \pm 63, \pm \frac{1}{2}, \pm \frac{3}{2}, \pm \frac{7}{2}, \pm \frac{9}{2}, \pm \frac{21}{2}, \pm \frac{63}{2}

Step 4: Verify the zeros shown on the graph

Based on the graph description, the zeros of the function f(x)f(x) are:

x = -1, \quad x = 1.5 \quad \text{(or \frac{3}{2})}, \quad x = 3

Now let's check if these values are in our list of possible rational zeros:

  • x=1x = -1 is in the list.
  • x=32x = \frac{3}{2} (which is 1.51.5) is in the list.
  • x=3x = 3 is in the list.

Thus, all zeros of f(x)f(x) shown on the graph are contained in our list of possible rational zeros.

Final Answer:

The possible rational zeros of f(x)f(x) are:

±1,±3,±7,±9,±21,±63,±12,±32,±72,±92,±212,±632\pm 1, \pm 3, \pm 7, \pm 9, \pm 21, \pm 63, \pm \frac{1}{2}, \pm \frac{3}{2}, \pm \frac{7}{2}, \pm \frac{9}{2}, \pm \frac{21}{2}, \pm \frac{63}{2}

Would you like further explanation or details on any step?

Here are five related questions to expand on this topic:

  1. How do you apply synthetic division to verify which possible rational zeros are actual zeros?
  2. How do you use Descartes' Rule of Signs to predict the number of positive and negative real zeros?
  3. What is the significance of the multiplicity of zeros in the graph of a polynomial function?
  4. How do you factor a polynomial after finding one rational zero?
  5. What is the difference between rational zeros and irrational zeros in terms of solving polynomials?

Tip: The Rational Root Theorem is useful when working with polynomials with integer coefficients, as it gives a manageable list of possible rational solutions.

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Math Problem Analysis

Mathematical Concepts

Polynomial Functions
Rational Zero Theorem
Graph Analysis

Formulas

Rational Zero Theorem: p/q, where p is a factor of the constant term, and q is a factor of the leading coefficient

Theorems

Rational Zero Theorem

Suitable Grade Level

Grades 10-12