Math Problem Statement

Required information Skip to question Use the Newton-Raphson method to find the root of the function f(x) = e–0.5x(4 – x) – 2.

The Newton-Raphson method does not work when the initial guess is 6 because the derivative of the given function is negative at x0 = 6.

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Solution

The statement is True.

Let's break this down:

The Newton-Raphson method iteratively refines guesses for the root of the equation f(x)=0f(x) = 0. The method uses the formula:

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

Where:

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

For the Newton-Raphson method to work, the derivative f(x)f'(x) should not be zero or very close to zero, as this would cause division by zero or result in a very large update that could lead to divergence.

Given the function:

f(x)=e0.5x(4x)2f(x) = e^{-0.5x}(4 - x) - 2

The derivative f(x)f'(x) will involve both the product rule and the chain rule.

At x0=6x_0 = 6, if the derivative f(6)f'(6) is negative, the Newton-Raphson method could still work mathematically (since it is defined as long as the derivative is not zero), but a negative value of f(x0)f'(x_0) might lead to undesirable behavior or poor convergence depending on the function's behavior.

To confirm this specifically, we'd need to compute f(x)f'(x) at x0=6x_0 = 6 and check whether the derivative is negative. However, the general idea is that the Newton-Raphson method may not work well for certain initial guesses if the derivative is negative or close to zero, as the sign of the update can cause erratic behavior.

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Math Problem Analysis

Mathematical Concepts

Numerical Methods
Newton-Raphson Method
Derivatives

Formulas

Newton-Raphson iteration formula: x_{n+1} = x_n - f(x_n)/f'(x_n)

Theorems

Newton-Raphson Convergence Criteria

Suitable Grade Level

Undergraduate Level (Numerical Methods, Calculus)