Math Problem Statement

Solve the equation x^3 + 2x^2 - 5x - 6 = 0 given that 2 is a zero of f(x).

Solution

We are asked to solve the cubic equation:

x3+2x25x6=0x^3 + 2x^2 - 5x - 6 = 0

with the given information that x=2x = 2 is a root.

Steps:

  1. Verify the root:
    Substitute x=2x = 2 into the equation:

    23+2(22)5(2)6=8+8106=02^3 + 2(2^2) - 5(2) - 6 = 8 + 8 - 10 - 6 = 0

    Since this holds true, x=2x = 2 is indeed a root.

  2. Factor the polynomial using synthetic division:
    Since x=2x = 2 is a root, we can divide the cubic polynomial by x2x - 2.

    Perform synthetic division on x3+2x25x6x^3 + 2x^2 - 5x - 6 by x2x - 2:

    2 | 1   2   -5   -6
        |     2    8    6
        ----------------
          1   4    3    0
    

    The quotient is x2+4x+3x^2 + 4x + 3, and the remainder is 0.

  3. Factor the quadratic:
    Now we solve the quadratic x2+4x+3x^2 + 4x + 3 by factoring:

    x2+4x+3=(x+1)(x+3)x^2 + 4x + 3 = (x + 1)(x + 3)

  4. Find all the roots:
    The full factorization of the original polynomial is:

    (x2)(x+1)(x+3)=0(x - 2)(x + 1)(x + 3) = 0

    Therefore, the solutions are:

    x=2,x=1,x=3x = 2, \quad x = -1, \quad x = -3

Final Answer:

The solutions to the equation x3+2x25x6=0x^3 + 2x^2 - 5x - 6 = 0 are:

x=2,x=1,x=3x = 2, \quad x = -1, \quad x = -3

Would you like further details or have any questions?


Here are five related questions to explore further:

  1. How does synthetic division work, and why is it useful in solving cubic equations?
  2. What other methods can be used to solve cubic equations if a root is not given?
  3. Can you always factor a cubic polynomial into linear factors if all roots are real?
  4. How can the quadratic formula be applied if the quadratic part isn't factorable?
  5. What are some real-world applications of solving cubic equations?

Tip: Always verify your roots by substituting them back into the original equation!

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Math Problem Analysis

Mathematical Concepts

Algebra
Polynomial equations
Factoring
Synthetic division

Formulas

Cubic polynomial factorization
Quadratic equation factoring

Theorems

Fundamental Theorem of Algebra
Remainder Theorem

Suitable Grade Level

Grades 10-12