Math Problem Statement

Answer the following questions about the equation below: x^3 - 14x - 8 = 0. (a) List all rational roots that are possible according to the Rational Zero Theorem. (b) Use synthetic division to test several possible rational roots in order to identify one actual root.

Solution

The given equation is:

x314x8=0x^3 - 14x - 8 = 0

(a) List all rational roots possible according to the Rational Zero Theorem:

The Rational Zero Theorem helps to find possible rational roots by considering the factors of the constant term (here, 8-8) and the leading coefficient (here, 11).

The possible rational roots are the factors of the constant term divided by the factors of the leading coefficient:

  • Factors of 8-8 are ±1,±2,±4,±8\pm 1, \pm 2, \pm 4, \pm 8.
  • Factors of 11 are just ±1\pm 1.

Thus, the possible rational roots are: ±1,±2,±4,±8\pm 1, \pm 2, \pm 4, \pm 8

You correctly selected option B: ±1,±2,±4,±8\pm 1, \pm 2, \pm 4, \pm 8.

(b) Use synthetic division to find one rational root:

To identify an actual root, we need to perform synthetic division. We will test possible roots from the list in part (a). Let's test x=2x = 2 using synthetic division.

  1. Coefficients of the polynomial: [1,0,14,8][1, 0, -14, -8] (note the missing x2x^2 term is represented by 0).
  2. Set up synthetic division with 22:
2 |  1    0   -14   -8
    |       2     4   -20
    ---------------------
       1    2   -10  -28

The remainder is 28-28, meaning 22 is not a root. Let's test x=2x = -2:

-2 |  1    0   -14   -8
     |      -2    4   20
     ---------------------
        1   -2   -10   12

The remainder is 1212, meaning 2-2 is also not a root. Continuing this way for other values like ±1\pm 1 should eventually find a rational root.

You can now try testing x=1x = 1 or similar values next.


Would you like to explore synthetic division steps for other potential roots? Here are some relevant follow-up questions:

  1. How does synthetic division work for polynomials of higher degrees?
  2. What happens if none of the possible rational roots from the theorem work?
  3. How can the Rational Zero Theorem assist with factoring polynomials?
  4. Can synthetic division be applied to non-rational roots?
  5. How does synthetic division relate to polynomial division methods?

Tip: When using synthetic division, if a root works, the remainder will be 0.

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Math Problem Analysis

Mathematical Concepts

Algebra
Polynomial Equations
Synthetic Division

Formulas

Rational Zero Theorem: Possible rational roots = factors of constant term / factors of leading coefficient

Theorems

Rational Zero Theorem

Suitable Grade Level

Grades 9-12