Math Problem Statement

Find all zeros of the function f(x) = 8x^3 - 2x^2 - 15x + 9. Enter the zeros separated by commas.

Solution

The problem requires finding all zeros of the polynomial function:

f(x)=8x32x215x+9f(x) = 8x^3 - 2x^2 - 15x + 9

Steps to Solve:

  1. Identify possible rational roots using the Rational Root Theorem: The possible roots are ±pq\pm \frac{p}{q}, where pp is a factor of the constant term (9) and qq is a factor of the leading coefficient (8). The possible rational roots are:

    ±1,±12,±14,±18,±3,±32,±34,±38,±9,±92,±94,±98\pm 1, \pm \frac{1}{2}, \pm \frac{1}{4}, \pm \frac{1}{8}, \pm 3, \pm \frac{3}{2}, \pm \frac{3}{4}, \pm \frac{3}{8}, \pm 9, \pm \frac{9}{2}, \pm \frac{9}{4}, \pm \frac{9}{8}

  2. Test rational roots: Substitute the possible roots into the function f(x)f(x). After testing, we find that x=32x = \frac{3}{2} is a root.

  3. Perform synthetic division: Divide f(x)f(x) by x32x - \frac{3}{2} to reduce the degree of the polynomial.

    Result of division: f(x)=(x32)(8x2+10x6)f(x) = \left(x - \frac{3}{2}\right)\left(8x^2 + 10x - 6\right)

  4. Solve the quadratic 8x2+10x6=08x^2 + 10x - 6 = 0 using the quadratic formula: x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} Substituting a=8a = 8, b=10b = 10, and c=6c = -6: x=10±1024(8)(6)2(8)x = \frac{-10 \pm \sqrt{10^2 - 4(8)(-6)}}{2(8)} x=10±100+19216x = \frac{-10 \pm \sqrt{100 + 192}}{16} x=10±29216x = \frac{-10 \pm \sqrt{292}}{16} Simplify: x=10±27316=5±738x = \frac{-10 \pm 2\sqrt{73}}{16} = \frac{-5 \pm \sqrt{73}}{8}

Final Zeros:

x=32,x=5+738,x=5738x = \frac{3}{2}, \quad x = \frac{-5 + \sqrt{73}}{8}, \quad x = \frac{-5 - \sqrt{73}}{8}

Would you like further explanation or a step-by-step breakdown of any part?

Related Questions:

  1. How does the Rational Root Theorem help in solving polynomial equations?
  2. What are other methods for finding roots of polynomials?
  3. Why is synthetic division useful for simplifying polynomials?
  4. How do irrational roots affect the solution of a polynomial equation?
  5. Can complex roots occur in a cubic polynomial, and how would they be

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Math Problem Analysis

Mathematical Concepts

Polynomials
Synthetic Division
Quadratic Equations
Roots of Functions

Formulas

Quadratic formula: x = (-b ± √(b² - 4ac)) / 2a
Rational Root Theorem

Theorems

Rational Root Theorem

Suitable Grade Level

Grades 10-12