Math Problem Statement

You can use the recursion x_n = (x_{n-1} + 10 / x_{n-1}) / 2 and the process of iteration to estimate the value of sqrt(10) without using a calculator. What is the value of the 2nd iterate if x_0 = 3.1? Carry out your answers to the 5th decimal place.

Solution

This question asks us to calculate the second iterate (x2x_2) of a given recursive formula to estimate 10\sqrt{10}, starting from an initial guess x0=3.1x_0 = 3.1. The recursive formula provided is:

xn=xn1+10xn12.x_n = \frac{x_{n-1} + \frac{10}{x_{n-1}}}{2}.

Let's compute x1x_1 and then x2x_2 step by step.

Step 1: Calculate x1x_1

Substitute x0=3.1x_0 = 3.1 into the formula: x1=3.1+103.12.x_1 = \frac{3.1 + \frac{10}{3.1}}{2}.

First, compute 103.1\frac{10}{3.1}: 103.13.22581.\frac{10}{3.1} \approx 3.22581.

Now add 3.13.1 to 3.225813.22581: 3.1+3.22581=6.32581.3.1 + 3.22581 = 6.32581.

Divide by 2: x1=6.3258123.16291.x_1 = \frac{6.32581}{2} \approx 3.16291.

Step 2: Calculate x2x_2

Use x13.16291x_1 \approx 3.16291 in the formula: x2=3.16291+103.162912.x_2 = \frac{3.16291 + \frac{10}{3.16291}}{2}.

First, compute 103.16291\frac{10}{3.16291}: 103.162913.16202.\frac{10}{3.16291} \approx 3.16202.

Now add 3.162913.16291 to 3.162023.16202: 3.16291+3.16202=6.32493.3.16291 + 3.16202 = 6.32493.

Divide by 2: x2=6.3249323.16227.x_2 = \frac{6.32493}{2} \approx 3.16227.

Final Answer:

The second iterate is approximately: x2=3.16227.\boxed{x_2 = 3.16227}.

Would you like further explanation or verification?


Here are 5 related questions for further exploration:

  1. How does the recursive formula for estimating square roots converge to the actual value?
  2. Why is it important to carry out calculations to multiple decimal places in iterative methods?
  3. Can this formula be used to estimate 20\sqrt{20}? How would it differ?
  4. What is the significance of the initial guess (x0x_0) in the speed of convergence?
  5. How would the error between iterations be calculated in this case?

Tip: Iterative methods often improve accuracy significantly with each step, but watch for computational round-off errors in practical applications!

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Math Problem Analysis

Mathematical Concepts

Iteration
Square Roots
Algebra

Formulas

x_n = (x_{n-1} + 10 / x_{n-1}) / 2

Theorems

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Suitable Grade Level

Grades 10-12