Math Problem Statement

An iterative formula is shown below. x_{n+1} = \frac{x_n}{2} + \frac{1}{x_n} Starting with x_1 = 10, work out the values of x_3 and x_4. Give your answers to 1 d.p.

Solution

The problem involves an iterative formula:

xn+1=xn2+1xnx_{n+1} = \frac{x_n}{2} + \frac{1}{x_n}

Starting with x1=10x_1 = 10, we are tasked to calculate x3x_3 and x4x_4, rounding the results to 1 decimal place.


Step-by-step solution:

  1. Start with x1=10x_1 = 10: This is the given initial value.

  2. Calculate x2x_2: Using the formula: x2=x12+1x1x_2 = \frac{x_1}{2} + \frac{1}{x_1} Substituting x1=10x_1 = 10: x2=102+110=5+0.1=5.1x_2 = \frac{10}{2} + \frac{1}{10} = 5 + 0.1 = 5.1

  3. Calculate x3x_3: Using the formula: x3=x22+1x2x_3 = \frac{x_2}{2} + \frac{1}{x_2} Substituting x2=5.1x_2 = 5.1: x3=5.12+15.1=2.55+0.196=2.746x_3 = \frac{5.1}{2} + \frac{1}{5.1} = 2.55 + 0.196 = 2.746 Rounding to 1 decimal place: x3=2.7x_3 = 2.7

  4. Calculate x4x_4: Using the formula: x4=x32+1x3x_4 = \frac{x_3}{2} + \frac{1}{x_3} Substituting x3=2.7x_3 = 2.7: x4=2.72+12.7=1.35+0.370=1.72x_4 = \frac{2.7}{2} + \frac{1}{2.7} = 1.35 + 0.370 = 1.72 Rounding to 1 decimal place: x4=1.7x_4 = 1.7


Final answers:

  • x3=2.7x_3 = 2.7
  • x4=1.7x_4 = 1.7

Would you like further clarification or assistance with related problems?


Related Questions:

  1. How does the iterative method converge for different starting values of x1x_1?
  2. What is the mathematical significance of this iterative formula?
  3. Can you generalize the process to find xnx_n for any nn?
  4. What happens if x1x_1 is a very small number like 0.10.1?
  5. How can this iteration be used to approximate square roots?

Tip:

When solving iterative formulas, always keep intermediate calculations accurate before rounding to ensure precise results in subsequent steps!

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Math Problem Analysis

Mathematical Concepts

Iteration
Sequences
Algebra

Formulas

x_{n+1} = \frac{x_n}{2} + \frac{1}{x_n}

Theorems

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Suitable Grade Level

Grades 9-11