5) Use antiderivatives to find f(x) given f'(x) = a and f (9) = 8.

Calculus: Early Transcendentals
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Author:James Stewart
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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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**Problem 5: Antiderivatives and Initial Conditions**

**Objective:**
Determine the function \( f(x) \) using antiderivatives, given that its derivative is \( f'(x) = \frac{1}{\sqrt{x}} \) and it satisfies the condition \( f(9) = 8 \).

**Solution Outline:**

1. **Find the Antiderivative:**
   - Start by integrating the derivative \( f'(x) = \frac{1}{\sqrt{x}} \).
   - Rewrite \( \frac{1}{\sqrt{x}} \) as \( x^{-\frac{1}{2}} \).
   - Integrate \( x^{-\frac{1}{2}} \) to find \( f(x) \):
     \[
     \int x^{-\frac{1}{2}} \, dx = 2x^{\frac{1}{2}} + C
     \]
   - Thus, the general solution is \( f(x) = 2\sqrt{x} + C \).

2. **Apply the Initial Condition:**
   - Use the given condition \( f(9) = 8 \) to solve for \( C \).
   - Substitute \( x = 9 \) into the general solution:
     \[
     8 = 2\sqrt{9} + C
     \]
   - Simplify and solve for \( C \):
     \[
     8 = 2 \times 3 + C \Rightarrow 8 = 6 + C \Rightarrow C = 2
     \]

3. **Final Solution:**
   - Substitute \( C = 2 \) back into the general solution:
     \[
     f(x) = 2\sqrt{x} + 2
     \]

**Conclusion:**
The function \( f(x) = 2\sqrt{x} + 2 \) satisfies both the derivative condition and the initial condition given.
Transcribed Image Text:**Problem 5: Antiderivatives and Initial Conditions** **Objective:** Determine the function \( f(x) \) using antiderivatives, given that its derivative is \( f'(x) = \frac{1}{\sqrt{x}} \) and it satisfies the condition \( f(9) = 8 \). **Solution Outline:** 1. **Find the Antiderivative:** - Start by integrating the derivative \( f'(x) = \frac{1}{\sqrt{x}} \). - Rewrite \( \frac{1}{\sqrt{x}} \) as \( x^{-\frac{1}{2}} \). - Integrate \( x^{-\frac{1}{2}} \) to find \( f(x) \): \[ \int x^{-\frac{1}{2}} \, dx = 2x^{\frac{1}{2}} + C \] - Thus, the general solution is \( f(x) = 2\sqrt{x} + C \). 2. **Apply the Initial Condition:** - Use the given condition \( f(9) = 8 \) to solve for \( C \). - Substitute \( x = 9 \) into the general solution: \[ 8 = 2\sqrt{9} + C \] - Simplify and solve for \( C \): \[ 8 = 2 \times 3 + C \Rightarrow 8 = 6 + C \Rightarrow C = 2 \] 3. **Final Solution:** - Substitute \( C = 2 \) back into the general solution: \[ f(x) = 2\sqrt{x} + 2 \] **Conclusion:** The function \( f(x) = 2\sqrt{x} + 2 \) satisfies both the derivative condition and the initial condition given.
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