Math Problem Statement

x^3+x^2-2x-8

Solution

You provided the polynomial:

P(x)=x3+x22x8P(x) = x^3 + x^2 - 2x - 8

Step 1: Check for Rational Roots

Using the Rational Root Theorem, the possible rational roots are the factors of 8-8 (constant term) divided by the factors of 11 (leading coefficient):

±1,±2,±4,±8\pm 1, \pm 2, \pm 4, \pm 8

Let's test x=2x = 2:

(2)3+(2)22(2)8=8+448=0(2)^3 + (2)^2 - 2(2) - 8 = 8 + 4 - 4 - 8 = 0

Since x=2x = 2 is a root, we can factor x2x - 2 from P(x)P(x).

Step 2: Polynomial Division

Dividing P(x)P(x) by (x2)(x - 2) using synthetic division:

  2 |  1   1  -2  -8  
    |      2   6   8  
  ------------------
      1   3   4   0  

The quotient is:

x2+3x+4x^2 + 3x + 4

Step 3: Solve x2+3x+4=0x^2 + 3x + 4 = 0

Using the quadratic formula:

x=3±324(1)(4)2(1)x = \frac{-3 \pm \sqrt{3^2 - 4(1)(4)}}{2(1)}

x=3±9162x = \frac{-3 \pm \sqrt{9 - 16}}{2}

x=3±72x = \frac{-3 \pm \sqrt{-7}}{2}

Since 7\sqrt{-7} is imaginary, the remaining roots are:

x=3±i72x = \frac{-3 \pm i\sqrt{7}}{2}

Final Answer:

The factorization of P(x)P(x):

(x2)(x2+3x+4)(x - 2) \left(x^2 + 3x + 4\right)

The roots:

x=2,x=3+i72,x=3i72x = 2, \quad x = \frac{-3 + i\sqrt{7}}{2}, \quad x = \frac{-3 - i\sqrt{7}}{2}


Would you like more details or have any questions?

Related Questions:

  1. How does the Rational Root Theorem help in solving polynomials?
  2. What are the steps for performing synthetic division?
  3. How do you solve quadratic equations with complex roots?
  4. Can this polynomial be solved using another method, such as factoring by grouping?
  5. How do complex roots always appear in conjugate pairs?

Tip: Always check for rational roots first using the Rational Root Theorem—it simplifies polynomial solving significantly!

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Math Problem Analysis

Mathematical Concepts

Polynomials
Rational Root Theorem
Synthetic Division
Quadratic Equations
Complex Roots

Formulas

Rational Root Theorem: Possible rational roots are factors of the constant term divided by factors of the leading coefficient.
Quadratic Formula: x = (-b ± √(b^2 - 4ac)) / 2a

Theorems

Rational Root Theorem
Quadratic Formula

Suitable Grade Level

Grades 9-12