Math Problem Statement

You wish to use Newton's Method to approximate the root of f(x) = 6x^2 - 1/x. If you begin with an initial value of x1 = 1, what will be the value of the second iteration of Newton's Method? That is, what will be the value of x3?

Solution

This problem requires using Newton's Method to approximate the root of the given function f(x)=6x21xf(x) = 6x^2 - \frac{1}{x}.

Newton's Method Formula:

Newton's Method formula for approximating roots is:

xn+1=xnf(xn)f(xn)x_{n+1} = x_n - \frac{f(x_n)}{f'(x_n)}

Where:

  • xnx_n is the current approximation,
  • xn+1x_{n+1} is the next approximation,
  • f(x)f(x) is the function,
  • f(x)f'(x) is the derivative of the function.

Step 1: Compute the derivative of f(x)f(x)

Given f(x)=6x21xf(x) = 6x^2 - \frac{1}{x}, we can calculate the derivative:

f(x)=ddx(6x21x)=12x+1x2f'(x) = \frac{d}{dx} \left( 6x^2 - \frac{1}{x} \right) = 12x + \frac{1}{x^2}

Step 2: Apply Newton's Method for the first iteration

We are given x1=1x_1 = 1.

  1. Compute f(x1)f(x_1): f(1)=6(1)211=61=5f(1) = 6(1)^2 - \frac{1}{1} = 6 - 1 = 5

  2. Compute f(x1)f'(x_1): f(1)=12(1)+1(1)2=12+1=13f'(1) = 12(1) + \frac{1}{(1)^2} = 12 + 1 = 13

  3. Calculate x2x_2: x2=x1f(x1)f(x1)=1513=10.384615=0.615385x_2 = x_1 - \frac{f(x_1)}{f'(x_1)} = 1 - \frac{5}{13} = 1 - 0.384615 = 0.615385

Step 3: Apply Newton's Method for the second iteration

Now we use x2=0.615385x_2 = 0.615385 to find x3x_3.

  1. Compute f(x2)f(x_2): f(0.615385)=6(0.615385)210.6153856(0.378553)1.6252.271321.625=0.64632f(0.615385) = 6(0.615385)^2 - \frac{1}{0.615385} \approx 6(0.378553) - 1.625 \approx 2.27132 - 1.625 = 0.64632

  2. Compute f(x2)f'(x_2): f(0.615385)=12(0.615385)+1(0.615385)27.38462+2.637610.0222f'(0.615385) = 12(0.615385) + \frac{1}{(0.615385)^2} \approx 7.38462 + 2.6376 \approx 10.0222

  3. Calculate x3x_3: x3=x2f(x2)f(x2)=0.6153850.6463210.02220.6153850.0645=0.55087x_3 = x_2 - \frac{f(x_2)}{f'(x_2)} = 0.615385 - \frac{0.64632}{10.0222} \approx 0.615385 - 0.0645 = 0.55087

Final Answer:

The value of x3x_3 is approximately 0.55087.


Would you like a detailed explanation of any specific step, or do you have any further questions?

Here are 5 related questions to extend your understanding:

  1. How does Newton's Method converge to the root of a function?
  2. What are the conditions for Newton's Method to work effectively?
  3. Can you always rely on Newton's Method to find a root?
  4. What happens if you choose a bad initial approximation for Newton's Method?
  5. How does Newton's Method differ from other root-finding methods like the Bisection Method?

Tip: Newton's Method requires a good initial guess for fast convergence; otherwise, it may diverge or fail.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Calculus
Newton's Method
Derivatives
Root-finding algorithms

Formulas

Newton's Method: x_{n+1} = x_n - f(x_n)/f'(x_n)
Derivative of f(x) = 6x^2 - 1/x: f'(x) = 12x + 1/x^2

Theorems

Newton's Method Theorem
Derivative Rules

Suitable Grade Level

Undergraduate Calculus