Math Problem Statement

Starting with x = 5, use the iterative process to find an approximate solution to x³ - 5x² - 9 = 0. Give your answer to 2 decimal places.

Solution

To solve the problem using the iterative process described for the equation:

x35x29=0x^3 - 5x^2 - 9 = 0

The iteration formula provided is:

x=5+9x2.x = 5 + \frac{9}{x^2}.

We are starting with x=5x = 5, and the process involves repeating the steps until the value of xx stabilizes (rounded to 2 decimal places). Let me calculate the approximate solution iteratively for you:


Step 1: Start with x0=5x_0 = 5.

Step 2: Use the iteration formula to find the next value:

xn+1=5+9xn2.x_{n+1} = 5 + \frac{9}{x_n^2}.


Iterations:

  1. Iteration 1 (Starting with x0=5x_0 = 5): x1=5+952=5+925=5+0.36=5.36x_1 = 5 + \frac{9}{5^2} = 5 + \frac{9}{25} = 5 + 0.36 = 5.36

  2. Iteration 2 (Using x1=5.36x_1 = 5.36): x2=5+9(5.36)2.x_2 = 5 + \frac{9}{(5.36)^2}. First, calculate 5.3625.36^2: 5.362=28.7296.5.36^2 = 28.7296. Now: x2=5+928.7296=5+0.3132=5.3132(rounded to 4 d.p.).x_2 = 5 + \frac{9}{28.7296} = 5 + 0.3132 = 5.3132 \quad (\text{rounded to 4 d.p.}).

  3. Iteration 3 (Using x2=5.3132x_2 = 5.3132): x3=5+9(5.3132)2.x_3 = 5 + \frac{9}{(5.3132)^2}. First, calculate 5.313225.3132^2: 5.31322=28.2339.5.3132^2 = 28.2339. Now: x3=5+928.2339=5+0.3189=5.3189.x_3 = 5 + \frac{9}{28.2339} = 5 + 0.3189 = 5.3189.

  4. Iteration 4 (Using x3=5.3189x_3 = 5.3189): x4=5+9(5.3189)2.x_4 = 5 + \frac{9}{(5.3189)^2}. First, calculate 5.318925.3189^2: 5.31892=28.2866.5.3189^2 = 28.2866. Now: x4=5+928.2866=5+0.3182=5.3182.x_4 = 5 + \frac{9}{28.2866} = 5 + 0.3182 = 5.3182.


Rounding to 2 Decimal Places:

At this point:

  • x3=5.32x_3 = 5.32
  • x4=5.32x_4 = 5.32.

The values stabilize at x=5.32x = 5.32 (to 2 d.p.).


Final Answer:

The approximate solution to x35x29=0x^3 - 5x^2 - 9 = 0 is:

5.32\boxed{5.32}

Would you like a step-by-step explanation for any part of this process or further clarification?


Related Questions:

  1. How can this iterative process be generalized for other equations?
  2. What happens if we start with a different initial guess?
  3. Can the iteration formula fail to converge? Under what conditions?
  4. How is this iteration process related to fixed-point iteration?
  5. How can we graphically interpret the convergence of the solution?

Tip:

The accuracy of the iterative process depends heavily on the starting value and the behavior of the function. Always check the convergence of the iterations.

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Math Problem Analysis

Mathematical Concepts

Iterative Methods
Algebra
Cubic Equations

Formulas

x = 5 + 9 / x²

Theorems

Fixed-Point Iteration

Suitable Grade Level

Grades 10-12