Math Problem Statement

Find the limit \( \lim_{h \to 0} \frac{f(x+h) - f(x)}{h} \) for the function \( f(x) = \frac{x^3}{3} - x \).

Solution

The image contains a mathematical problem involving the derivative of a given function, along with some handwritten notes. Let's break it down:

Problem Statement:

Given the function f(x)=x33xf(x) = \frac{x^3}{3} - x, find limh0f(x+h)f(x)h\lim_{{h \to 0}} \frac{f(x+h) - f(x)}{h}.

This expression represents the definition of the derivative of f(x)f(x) at any point xx.

Steps to Solve:

  1. Substitute f(x+h)f(x+h): f(x+h)=(x+h)33(x+h)f(x+h) = \frac{(x+h)^3}{3} - (x+h)

  2. Expand (x+h)3(x+h)^3: (x+h)3=x3+3x2h+3xh2+h3(x+h)^3 = x^3 + 3x^2h + 3xh^2 + h^3 Therefore: f(x+h)=x3+3x2h+3xh2+h33(x+h)f(x+h) = \frac{x^3 + 3x^2h + 3xh^2 + h^3}{3} - (x+h)

  3. Simplify: f(x+h)=x33+x2h+xh23+h33xhf(x+h) = \frac{x^3}{3} + x^2h + \frac{xh^2}{3} + \frac{h^3}{3} - x - h

  4. Compute f(x+h)f(x)f(x+h) - f(x): f(x+h)f(x)=(x33+x2h+xh23+h33xh)(x33x)f(x+h) - f(x) = \left(\frac{x^3}{3} + x^2h + \frac{xh^2}{3} + \frac{h^3}{3} - x - h\right) - \left(\frac{x^3}{3} - x\right) Simplifying further: f(x+h)f(x)=x2h+xh23+h33hf(x+h) - f(x) = x^2h + \frac{xh^2}{3} + \frac{h^3}{3} - h

  5. Divide by hh: f(x+h)f(x)h=x2+xh23h+h33h1\frac{f(x+h) - f(x)}{h} = x^2 + \frac{xh^2}{3h} + \frac{h^3}{3h} - 1 Simplify: f(x+h)f(x)h=x2+xh3+h231\frac{f(x+h) - f(x)}{h} = x^2 + \frac{xh}{3} + \frac{h^2}{3} - 1

  6. Take the limit as h0h \to 0: limh0f(x+h)f(x)h=x21\lim_{{h \to 0}} \frac{f(x+h) - f(x)}{h} = x^2 - 1

Thus, the derivative of f(x)f(x) is f(x)=x21f'(x) = x^2 - 1.

Interpretation:

This means the rate of change of the function f(x)=x33xf(x) = \frac{x^3}{3} - x with respect to xx is x21x^2 - 1.


Would you like more details on this problem or have any other questions? Here are 5 questions that expand on this information:

  1. What is the geometric interpretation of the derivative f(x)f'(x) for the given function?
  2. How would you find the points where the derivative f(x)=0f'(x) = 0?
  3. How does the derivative relate to the concavity of the function f(x)f(x)?
  4. What would the second derivative f(x)f''(x) tell you about the function's behavior?
  5. How would you apply this derivative in a real-world problem involving rates of change?

Tip: Understanding the derivative as a limit is crucial, as it forms the foundation for more complex calculus concepts like integration and differential equations.

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Math Problem Analysis

Mathematical Concepts

Calculus
Limits
Derivatives

Formulas

Derivative definition: \( \lim_{h \to 0} \frac{f(x+h) - f(x)}{h} \)
Function expansion: \( (x+h)^3 = x^3 + 3x^2h + 3xh^2 + h^3 \)

Theorems

Limit Theorem
Basic Derivative Rules

Suitable Grade Level

Grades 11-12 or Early College