Find the linear approximation of f(x)=ln⁡x at x=7 and use it to approximate ln⁡(7.05).   L(x)=? x + ? ln⁡(7.05) ≈ ?

Calculus: Early Transcendentals
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Author:James Stewart
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Chapter1: Functions And Models
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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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Find the linear approximation of f(x)=ln⁡x at x=7 and use it to approximate ln⁡(7.05).
 
L(x)=? x + ?
ln⁡(7.05) ≈ ?
 
 
 
### Linear Approximation of Logarithmic Functions

**Problem Statement:**

Find the linear approximation of \( f(x) = \ln x \) at \( x = 7 \) and use it to approximate \(\ln(7.05)\).

**Solution:**

The linear approximation \( L(x) \) of a function \( f(x) \) at a point \( x = a \) is given by:
\[ 
L(x) = f(a) + f'(a)(x - a) 
\]

In this case, 
- \( f(x) = \ln x \) 
- \( a = 7 \)

First, compute \( f'(x) \):
\[ 
f'(x) = \frac{1}{x}
\]

Now, apply the values:
- \( f(a) = \ln 7 \)
- \( f'(a) = \frac{1}{7} \)

The linear approximation is:
\[ 
L(x) = \ln 7 + \frac{1}{7}(x - 7) 
\]

**Approximation of \(\ln(7.05)\):**

Using the linear approximation for \( x = 7.05 \):
\[ 
L(7.05) = \ln 7 + \frac{1}{7}(7.05 - 7) 
\]

This simplifies to:
\[ 
\ln(7.05) \approx \ln 7 + \frac{0.05}{7} 
\]

**Conclusion:**

The approximate value of \(\ln(7.05)\) is:
\[ 
\ln(7.05) \approx 1.95123
\]

This linear approximation method provides a quick and easy way to estimate logarithmic values near a known point.
Transcribed Image Text:### Linear Approximation of Logarithmic Functions **Problem Statement:** Find the linear approximation of \( f(x) = \ln x \) at \( x = 7 \) and use it to approximate \(\ln(7.05)\). **Solution:** The linear approximation \( L(x) \) of a function \( f(x) \) at a point \( x = a \) is given by: \[ L(x) = f(a) + f'(a)(x - a) \] In this case, - \( f(x) = \ln x \) - \( a = 7 \) First, compute \( f'(x) \): \[ f'(x) = \frac{1}{x} \] Now, apply the values: - \( f(a) = \ln 7 \) - \( f'(a) = \frac{1}{7} \) The linear approximation is: \[ L(x) = \ln 7 + \frac{1}{7}(x - 7) \] **Approximation of \(\ln(7.05)\):** Using the linear approximation for \( x = 7.05 \): \[ L(7.05) = \ln 7 + \frac{1}{7}(7.05 - 7) \] This simplifies to: \[ \ln(7.05) \approx \ln 7 + \frac{0.05}{7} \] **Conclusion:** The approximate value of \(\ln(7.05)\) is: \[ \ln(7.05) \approx 1.95123 \] This linear approximation method provides a quick and easy way to estimate logarithmic values near a known point.
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