Math Problem Statement

Use synthetic division to show that x is a solution of the equation, and use the result to factor the polynomial completely. List all real solutions of the equation. (Enter your answers as a comma-separated list.) x^3 + 4x^2 − 2x − 8 = 0, x =root 2

Solution

To determine if x=2x = 2 is a solution of the equation x3+4x22x8=0x^3 + 4x^2 - 2x - 8 = 0, we will use synthetic division. Then, we will factor the polynomial completely and find all real solutions.

Step 1: Synthetic Division

We'll divide the polynomial x3+4x22x8x^3 + 4x^2 - 2x - 8 by x2x - 2 using synthetic division.

  1. Write down the coefficients of the polynomial x3+4x22x8x^3 + 4x^2 - 2x - 8:

    • Coefficients: 1,4,2,81, 4, -2, -8
  2. Set up the synthetic division with x=2x = 2 as follows:

2 & 1 & 4 & -2 & -8 \\ & & 2 & 12 & 20 \\ \hline & 1 & 6 & 10 & 0 \\ \end{array}$$ ### Step 2: Explanation of the Synthetic Division Process 1. Bring down the first coefficient, $$1$$, and place it under the line. 2. Multiply $$2$$ (the value of $$x$$) by $$1$$, which gives $$2$$, and write it under the next coefficient. 3. Add $$4 + 2 = 6$$. 4. Multiply $$2 \times 6 = 12$$ and write it under the next coefficient. 5. Add $$-2 + 12 = 10$$. 6. Multiply $$2 \times 10 = 20$$, and write it under the last coefficient. 7. Add $$-8 + 20 = 0$$, which is the remainder. Since the remainder is zero, $$x = 2$$ is a solution, and the quotient from the division is $$x^2 + 6x + 10$$. ### Step 3: Factor the Polynomial The result from the synthetic division gives us: $$x^3 + 4x^2 - 2x - 8 = (x - 2)(x^2 + 6x + 10)$$ Next, we attempt to factor $$x^2 + 6x + 10$$. However, this quadratic does not factor nicely using real numbers, so we apply the quadratic formula: $$x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$$ where $$a = 1$$, $$b = 6$$, and $$c = 10$$. $$x = \frac{-6 \pm \sqrt{6^2 - 4(1)(10)}}{2(1)} = \frac{-6 \pm \sqrt{36 - 40}}{2} = \frac{-6 \pm \sqrt{-4}}{2} = \frac{-6 \pm 2i}{2}$$ $$x = -3 \pm i$$ So, the quadratic $$x^2 + 6x + 10$$ has complex roots $$x = -3 + i$$ and $$x = -3 - i$$. ### Step 4: List All Real Solutions The only real solution is $$x = 2$$, and the complete factorization of the polynomial is: $$(x - 2)(x^2 + 6x + 10)$$ ### Final Answer: The real solution is: $$x = 2$$ Do you want more details or have any questions? Here are some related questions for further understanding: 1. How do you interpret complex roots geometrically? 2. What is the significance of the remainder being zero in synthetic division? 3. How do you determine whether a quadratic has real or complex solutions? 4. Can synthetic division be used to divide by any polynomial, or just linear ones? 5. How would you verify the factorization of a cubic polynomial? **Tip:** When using the quadratic formula, always check the discriminant $$\Delta = b^2 - 4ac$$ to determine the nature of the roots (real or complex).

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Math Problem Analysis

Mathematical Concepts

Algebra
Polynomials
Synthetic Division
Quadratic Equations
Complex Numbers

Formulas

Synthetic division: used to divide polynomials
Quadratic formula: x = (-b ± √(b^2 - 4ac)) / 2a

Theorems

Fundamental Theorem of Algebra
Quadratic formula

Suitable Grade Level

Grades 10-12