Math Problem Statement

The figure shows the graph of a function f. Suppose that Newton's method is used to approximate the solution s of the equation f(x) = 0 with initial approximation x₁ = 6. a. Draw the tangent lines that are used to find x₂ and x₃, and estimate the numerical values of x₂ and x₃. b. Would x₁ = 8 be a better first approximation? Explain.

Solution

Based on the provided image, let’s examine each part of the question:

Part (a)

This part involves using Newton's Method to approximate the solution ss of the equation f(x)=0f(x) = 0 with an initial approximation of x1=6x_1 = 6.

  1. Newton's Method Recap: Newton's Method iteratively approximates roots of a function f(x)f(x) by finding the tangent line at each approximation xnx_n and determining where this tangent line intersects the x-axis. The formula for Newton’s Method is: xn+1=xnf(xn)f(xn)x_{n+1} = x_n - \frac{f(x_n)}{f'(x_n)}

  2. Steps for Estimation:

    • The tangent line at x1=6x_1 = 6 should be drawn to estimate x2x_2, where it intersects the x-axis. From the image, it appears that x27.3x_2 \approx 7.3.
    • Similarly, the tangent line at x27.3x_2 \approx 7.3 should be drawn to estimate x3x_3, leading to x36.8x_3 \approx 6.8.

These tangent lines visually represent the iterative process of Newton’s Method, where each intersection point with the x-axis provides the next approximation.

Part (b)

For this part, we need to evaluate if starting with x1=8x_1 = 8 instead of x1=6x_1 = 6 would lead to a better approximation.

  1. Reasoning: Starting with x1=8x_1 = 8 could potentially be closer to the actual root ss as per the graph. From the visual assessment, it seems that x1=8x_1 = 8 is on the closer side of the root ss on the graph, making it likely that the Newton iteration will converge faster to the solution if started closer to the root.

Thus, the answer is Yes, x1=8x_1 = 8 would likely be a better first approximation since it is closer to the actual solution, minimizing the required iterations for convergence.


Would you like further details or explanations on any part?

Related Questions:

  1. How does the choice of the initial approximation x1x_1 affect the convergence of Newton's Method?
  2. Can Newton's Method fail to converge? Under what circumstances does this happen?
  3. What is the geometric interpretation of Newton's Method?
  4. How can one determine the function's derivative if it's not given explicitly?
  5. What are alternative methods to Newton's Method for finding roots of equations?

Tip:

In Newton's Method, a closer initial approximation to the actual root often results in faster convergence, but care must be taken as poor initial guesses can lead to divergence or convergence to a different root.

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Math Problem Analysis

Mathematical Concepts

Calculus
Newton's Method
Approximation of roots

Formulas

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

Theorems

Newton's Method

Suitable Grade Level

Undergraduate Calculus