Math Problem Statement

Let f(x)=x4−2. What is the value of x2 (the second approximation to the root of the equation f(x)=0) if you use Newton's method with x1=2?

Solution

To solve this using Newton's Method, the formula for the next approximation xn+1x_{n+1} is:

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

Given:

  • f(x)=x42f(x) = x^4 - 2,
  • Initial guess x1=2x_1 = 2.

Step 1: Compute f(x)f'(x)

The derivative of f(x)f(x) is: f(x)=4x3f'(x) = 4x^3

Step 2: Evaluate f(x1)f(x_1) and f(x1)f'(x_1)

For x1=2x_1 = 2: f(2)=242=162=14f(2) = 2^4 - 2 = 16 - 2 = 14 f(2)=4(23)=4(8)=32f'(2) = 4(2^3) = 4(8) = 32

Step 3: Compute x2x_2

Using the Newton's method formula: x2=x1f(x1)f(x1)x_2 = x_1 - \frac{f(x_1)}{f'(x_1)} Substitute the values: x2=21432=20.4375=1.5625x_2 = 2 - \frac{14}{32} = 2 - 0.4375 = 1.5625

Final Answer:

x2=1.5625x_2 = 1.5625

Let me know if you'd like further clarifications or additional examples! 😊

Related Questions:

  1. How does Newton's method work for non-polynomial functions?
  2. What happens if the initial guess is far from the actual root?
  3. Can Newton's method fail to converge? If so, why?
  4. How do you choose a good initial guess for Newton's method?
  5. What are some alternative methods for finding roots of functions?

Tip:

When using Newton's Method, always check f(x)f'(x) at your approximations. If it gets close to zero, the method can diverge or fail!

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Math Problem Analysis

Mathematical Concepts

Calculus
Root Approximation
Newton's Method

Formulas

x_{n+1} = x_n - f(x_n) / f'(x_n)

Theorems

Newton's Method for Root Finding

Suitable Grade Level

Grades 11-12 or College Level