Math Problem Statement

Use​ Newton's method to estimate the two zeros of the following function. Start with x 0equalsnegative 2 for the left zero and x 0equals3 for the right zero. Then for each​ case, find x 2. x minus x squared plus 8 Question content area bottom Part 1 If x 0equalsnegative 2​, then x 2equals    enter your response here. ​(Type an integer or a simplified​ fraction.)

Solution

Newton's method is an iterative method to approximate the roots of a function. It is defined as:

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

Given Function:

f(x)=xx2+8f(x) = x - x^2 + 8

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

f(x)=12xf'(x) = 1 - 2x

For x0=2x_0 = -2:

  1. Calculate f(x0)f(x_0) and f(x0)f'(x_0): f(2)=2(2)2+8=24+8=2f(-2) = -2 - (-2)^2 + 8 = -2 - 4 + 8 = 2 f(2)=12(2)=1+4=5f'(-2) = 1 - 2(-2) = 1 + 4 = 5

  2. Compute x1x_1: x1=x0f(x0)f(x0)=225=20.4=2.4x_1 = x_0 - \frac{f(x_0)}{f'(x_0)} = -2 - \frac{2}{5} = -2 - 0.4 = -2.4

  3. Calculate f(x1)f(x_1) and f(x1)f'(x_1): f(2.4)=2.4(2.4)2+8=2.45.76+8=0.16f(-2.4) = -2.4 - (-2.4)^2 + 8 = -2.4 - 5.76 + 8 = -0.16 f(2.4)=12(2.4)=1+4.8=5.8f'(-2.4) = 1 - 2(-2.4) = 1 + 4.8 = 5.8

  4. Compute x2x_2: x2=x1f(x1)f(x1)=2.40.165.8=2.4+0.027586=2.372414x_2 = x_1 - \frac{f(x_1)}{f'(x_1)} = -2.4 - \frac{-0.16}{5.8} = -2.4 + 0.027586 = -2.372414

Thus, for x0=2x_0 = -2, x22.372x_2 \approx -2.372.


For x0=3x_0 = 3:

  1. Calculate f(x0)f(x_0) and f(x0)f'(x_0): f(3)=332+8=39+8=2f(3) = 3 - 3^2 + 8 = 3 - 9 + 8 = 2 f(3)=12(3)=16=5f'(3) = 1 - 2(3) = 1 - 6 = -5

  2. Compute x1x_1: x1=x0f(x0)f(x0)=325=3+0.4=3.4x_1 = x_0 - \frac{f(x_0)}{f'(x_0)} = 3 - \frac{2}{-5} = 3 + 0.4 = 3.4

  3. Calculate f(x1)f(x_1) and f(x1)f'(x_1): f(3.4)=3.4(3.4)2+8=3.411.56+8=0.16f(3.4) = 3.4 - (3.4)^2 + 8 = 3.4 - 11.56 + 8 = -0.16 f(3.4)=12(3.4)=16.8=5.8f'(3.4) = 1 - 2(3.4) = 1 - 6.8 = -5.8

  4. Compute x2x_2: x2=x1f(x1)f(x1)=3.40.165.8=3.40.027586=3.372414x_2 = x_1 - \frac{f(x_1)}{f'(x_1)} = 3.4 - \frac{-0.16}{-5.8} = 3.4 - 0.027586 = 3.372414

Thus, for x0=3x_0 = 3, x23.372x_2 \approx 3.372.


Final Answers:

  1. For x0=2x_0 = -2, x22.372x_2 \approx -2.372.
  2. For x0=3x_0 = 3, x23.372x_2 \approx 3.372.

Would you like a detailed explanation of the iterations?
Here are 5 related questions:

  1. What is the significance of Newton's method in finding roots?
  2. Can Newton's method fail or converge slowly? When?
  3. What happens if we use a different starting value for this problem?
  4. How can we improve the accuracy of x2x_2 further?
  5. How does Newton's method compare to other root-finding methods like the bisection method?

Tip: Always check f(x)0f'(x) \neq 0 when using Newton's method to avoid division by zero!

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Math Problem Analysis

Mathematical Concepts

Calculus
Root-Finding Methods
Iterative Algorithms

Formulas

Newton's method formula: x_{n+1} = x_n - f(x_n)/f'(x_n)
Derivative: f'(x)

Theorems

Newton's Method Convergence

Suitable Grade Level

Grade 12 or First-Year University