Using the definition of the derivative, find f(x). Then find f'( – 6), f'(0), and f'(5) when the derivative exists. 72 X f(x) f'(x)= (Type an expression using x as the variable.) .…..

Calculus: Early Transcendentals
8th Edition
ISBN:9781285741550
Author:James Stewart
Publisher:James Stewart
Chapter1: Functions And Models
Section: Chapter Questions
Problem 1RCC: (a) What is a function? What are its domain and range? (b) What is the graph of a function? (c) How...
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**Title: Finding Derivatives Using the Definition of the Derivative**

**Introduction:**
In this tutorial, we will learn how to calculate the derivative of a function using the definition of the derivative. We will apply this method to the given function \( f(x) = \frac{72}{x} \). Additionally, we will find the derivative at specific points: \( f'(-6) \), \( f'(0) \), and \( f'(5) \), provided the derivative exists at those points.

**Problem Statement:**

Given the function:
\[ f(x) = \frac{72}{x} \]

1. Use the definition of the derivative to find \( f'(x) \).
2. Calculate \( f'(-6) \), \( f'(0) \), and \( f'(5) \), if the derivative exists at these points.

**Step-by-Step Solution:**

1. **Find \( f'(x) \) Using the Definition of the Derivative:**

   The definition of the derivative is given by:
   \[ f'(x) = \lim_{{h \to 0}} \frac{f(x+h) - f(x)}{h} \]

   For the function \( f(x) = \frac{72}{x} \), substitute \( f(x) \) and \( f(x+h) \):
   \[ f'(x) = \lim_{{h \to 0}} \frac{\frac{72}{x+h} - \frac{72}{x}}{h} \]

   Simplify the expression inside the limit by finding a common denominator for the fractions:
   \[ f'(x) = \lim_{{h \to 0}} \frac{72(x) - 72(x+h)}{h(x(x+h))} \]
   \[ f'(x) = \lim_{{h \to 0}} \frac{72x - 72x - 72h}{h(x^2 + xh)} \]
   \[ f'(x) = \lim_{{h \to 0}} \frac{-72h}{h(x^2 + xh)} \]
   
   Cancel \( h \) in the numerator and denominator:
   \[ f'(x) = \lim_{{h \to 0}} \frac{-72}{x^2 + xh} \
Transcribed Image Text:**Title: Finding Derivatives Using the Definition of the Derivative** **Introduction:** In this tutorial, we will learn how to calculate the derivative of a function using the definition of the derivative. We will apply this method to the given function \( f(x) = \frac{72}{x} \). Additionally, we will find the derivative at specific points: \( f'(-6) \), \( f'(0) \), and \( f'(5) \), provided the derivative exists at those points. **Problem Statement:** Given the function: \[ f(x) = \frac{72}{x} \] 1. Use the definition of the derivative to find \( f'(x) \). 2. Calculate \( f'(-6) \), \( f'(0) \), and \( f'(5) \), if the derivative exists at these points. **Step-by-Step Solution:** 1. **Find \( f'(x) \) Using the Definition of the Derivative:** The definition of the derivative is given by: \[ f'(x) = \lim_{{h \to 0}} \frac{f(x+h) - f(x)}{h} \] For the function \( f(x) = \frac{72}{x} \), substitute \( f(x) \) and \( f(x+h) \): \[ f'(x) = \lim_{{h \to 0}} \frac{\frac{72}{x+h} - \frac{72}{x}}{h} \] Simplify the expression inside the limit by finding a common denominator for the fractions: \[ f'(x) = \lim_{{h \to 0}} \frac{72(x) - 72(x+h)}{h(x(x+h))} \] \[ f'(x) = \lim_{{h \to 0}} \frac{72x - 72x - 72h}{h(x^2 + xh)} \] \[ f'(x) = \lim_{{h \to 0}} \frac{-72h}{h(x^2 + xh)} \] Cancel \( h \) in the numerator and denominator: \[ f'(x) = \lim_{{h \to 0}} \frac{-72}{x^2 + xh} \
For the given function, find (a) the equation of the secant line through the points where \( x \) has the given values and (b) the equation of the tangent line when \( x \) has the first value.

\[ y = f(x) = x^2 + x; \quad x = 3, \quad x = 5 \]

---

**a.** The equation of the secant line is \( y = \_\_\_ \)
Transcribed Image Text:For the given function, find (a) the equation of the secant line through the points where \( x \) has the given values and (b) the equation of the tangent line when \( x \) has the first value. \[ y = f(x) = x^2 + x; \quad x = 3, \quad x = 5 \] --- **a.** The equation of the secant line is \( y = \_\_\_ \)
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