Math Problem Statement

x^3-x-24=0 solve for x

Solution

To solve the cubic equation x3x24=0x^3 - x - 24 = 0, we can use a combination of methods, starting with trial and error for possible rational solutions, and then using techniques like synthetic division or factoring.

Step 1: Try Rational Roots

Using the Rational Root Theorem, the possible rational roots are the factors of the constant term (-24) divided by the factors of the leading coefficient (1). This gives us possible roots:

±1,±2,±3,±4,±6,±8,±12,±24\pm 1, \pm 2, \pm 3, \pm 4, \pm 6, \pm 8, \pm 12, \pm 24

Now, let's test these values by substituting them into the equation f(x)=x3x24f(x) = x^3 - x - 24.

  • For x=3x = 3: f(3)=33324=27324=0f(3) = 3^3 - 3 - 24 = 27 - 3 - 24 = 0

So, x=3x = 3 is a root.

Step 2: Factor the Cubic Equation

Now that we know x=3x = 3 is a root, we can factor x3x24x^3 - x - 24 as (x3)(quadratic expression)(x - 3)(\text{quadratic expression}).

Perform synthetic division to divide x3x24x^3 - x - 24 by x3x - 3:

3 & 1 & 0 & -1 & -24 \\ & & 3 & 9 & 24 \\ \hline & 1 & 3 & 8 & 0 \\ \end{array}$$ The quotient is $$x^2 + 3x + 8$$, so we have: $$x^3 - x - 24 = (x - 3)(x^2 + 3x + 8)$$ ### Step 3: Solve the Quadratic Equation Now, solve $$x^2 + 3x + 8 = 0$$ using the quadratic formula: $$x = \frac{-3 \pm \sqrt{3^2 - 4(1)(8)}}{2(1)}$$ $$x = \frac{-3 \pm \sqrt{9 - 32}}{2}$$ $$x = \frac{-3 \pm \sqrt{-23}}{2}$$ $$x = \frac{-3 \pm i\sqrt{23}}{2}$$ Thus, the solutions are: $$x = 3, \quad x = \frac{-3 + i\sqrt{23}}{2}, \quad x = \frac{-3 - i\sqrt{23}}{2}$$ ### Final Answer: The solutions to the equation $$x^3 - x - 24 = 0$$ are: $$x = 3, \quad x = \frac{-3 + i\sqrt{23}}{2}, \quad x = \frac{-3 - i\sqrt{23}}{2}$$ Would you like more details on any step or have any questions? --- Here are 5 related questions: 1. What is the Rational Root Theorem and how does it work? 2. How do you perform synthetic division? 3. How do you use the quadratic formula to solve any quadratic equation? 4. Can all cubic equations be solved by factoring? 5. What are complex numbers and how are they handled in equations? **Tip:** Always check for simple rational solutions first when dealing with cubic equations using the Rational Root Theorem.

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Math Problem Analysis

Mathematical Concepts

Cubic Equations
Rational Root Theorem
Synthetic Division
Quadratic Formula
Complex Numbers

Formulas

Cubic equation form: ax^3 + bx^2 + cx + d = 0
Quadratic formula: x = [-b ± √(b² - 4ac)] / 2a

Theorems

Rational Root Theorem
Quadratic Formula

Suitable Grade Level

Grades 10-12