Table of contents
- 0. Functions7h 52m
- Introduction to Functions16m
- Piecewise Functions10m
- Properties of Functions9m
- Common Functions1h 8m
- Transformations5m
- Combining Functions27m
- Exponent rules32m
- Exponential Functions28m
- Logarithmic Functions24m
- Properties of Logarithms34m
- Exponential & Logarithmic Equations35m
- Introduction to Trigonometric Functions38m
- Graphs of Trigonometric Functions44m
- Trigonometric Identities47m
- Inverse Trigonometric Functions48m
- 1. Limits and Continuity2h 2m
- 2. Intro to Derivatives1h 33m
- 3. Techniques of Differentiation3h 18m
- 4. Applications of Derivatives2h 38m
- 5. Graphical Applications of Derivatives6h 2m
- 6. Derivatives of Inverse, Exponential, & Logarithmic Functions2h 37m
- 7. Antiderivatives & Indefinite Integrals1h 26m
- 8. Definite Integrals4h 44m
- 9. Graphical Applications of Integrals2h 27m
- 10. Physics Applications of Integrals 2h 22m
4. Applications of Derivatives
Differentials
Problem 4.8.9
Textbook Question
{Use of Tech} Write the formula for Newton’s method and use the given initial approximation to compute the approximations x₁ and x₂.
f(x) = x² - 6; x₀ = 3

1
Newton's method is an iterative process used to approximate the roots of a real-valued function. The formula for Newton's method is: <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>x</mi><mo>_</mo><mi>n</mi><mo>+</mo><mn>1</mn><mo>=</mo><mi>x</mi><mo>_</mo><mi>n</mi><mo>-</mo><mfrac><mrow><mi>f</mi><mo>(</mo><mi>x</mi><mo>_</mo><mi>n</mi><mo>)</mo></mrow><mrow><mi>f</mi><mo>'</mo><mo>(</mo><mi>x</mi><mo>_</mo><mi>n</mi><mo>)</mo></mrow></mfrac></math>.
First, we need to find the derivative of the function <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>f</mi><mo>(</mo><mi>x</mi><mo>)</mo><mo>=</mo><msup><mi>x</mi><mn>2</mn></msup><mo>-</mo><mn>6</mn></math>. The derivative is <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>f</mi><mo>'</mo><mo>(</mo><mi>x</mi><mo>)</mo><mo>=</mo><mn>2</mn><mi>x</mi></math>.
Using the initial approximation <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>x</mi><mo>_</mo><mn>0</mn><mo>=</mo><mn>3</mn></math>, calculate <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>f</mi><mo>(</mo><mi>x</mi><mo>_</mo><mn>0</mn><mo>)</mo></math> and <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>f</mi><mo>'</mo><mo>(</mo><mi>x</mi><mo>_</mo><mn>0</mn><mo>)</mo></math>.
Substitute these values into the Newton's method formula to find <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>x</mi><mo>_</mo><mn>1</mn></math>: <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>x</mi><mo>_</mo><mn>1</mn><mo>=</mo><mi>x</mi><mo>_</mo><mn>0</mn><mo>-</mo><mfrac><mrow><mi>f</mi><mo>(</mo><mi>x</mi><mo>_</mo><mn>0</mn><mo>)</mo></mrow><mrow><mi>f</mi><mo>'</mo><mo>(</mo><mi>x</mi><mo>_</mo><mn>0</mn><mo>)</mo></mrow></mfrac></math>.
Repeat the process using <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>x</mi><mo>_</mo><mn>1</mn></math> to find <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>x</mi><mo>_</mo><mn>2</mn></math>: <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>x</mi><mo>_</mo><mn>2</mn><mo>=</mo><mi>x</mi><mo>_</mo><mn>1</mn><mo>-</mo><mfrac><mrow><mi>f</mi><mo>(</mo><mi>x</mi><mo>_</mo><mn>1</mn><mo>)</mo></mrow><mrow><mi>f</mi><mo>'</mo><mo>(</mo><mi>x</mi><mo>_</mo><mn>1</mn><mo>)</mo></mrow></mfrac></math>.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Newton's Method
Newton's Method is an iterative numerical technique used to find approximate solutions to equations. It starts with an initial guess and refines it using the formula x₁ = x₀ - f(x₀)/f'(x₀), where f'(x) is the derivative of the function. This method is particularly effective for functions that are continuous and differentiable near the root.
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Derivative
The derivative of a function measures how the function's output changes as its input changes. It is a fundamental concept in calculus that provides the slope of the tangent line to the function at any given point. In the context of Newton's Method, the derivative is crucial for determining the direction and magnitude of the adjustments made to the initial approximation.
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Initial Approximation
An initial approximation is the starting value used in iterative methods like Newton's Method. The choice of this value can significantly affect the convergence of the method to the actual root. A good initial approximation should be close to the actual root to ensure that the iterations lead to a successful and rapid convergence.
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