Show analytically (that is, without reference to a graph) that h(x) = v1 + x is always increasing, given that Dom h = [1,

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 Statement:**

Show analytically (that is, without reference to a graph) that \( h(x) = \sqrt{1 + x^3} \) is always increasing, given that \( \text{Dom } h = [1, \infty) \).

---

To demonstrate that the function \( h(x) \) is always increasing, you'll need to analyze its derivative \( h'(x) \). A function is increasing on an interval if its derivative is positive for all values in that interval.

1. **Differentiate \( h(x) \):**

   Apply the chain rule:
   \[
   h(x) = (1 + x^3)^{1/2}
   \]

   \[
   h'(x) = \frac{1}{2}(1 + x^3)^{-1/2} \cdot 3x^2 = \frac{3x^2}{2\sqrt{1 + x^3}}
   \]

2. **Analyze the derivative \( h'(x) \):**

   For the domain \( x \in [1, \infty) \):

   - The numerator, \( 3x^2 \), is always positive since \( x^2 \ge 0 \) and multiplying by 3 keeps it positive over the domain.
   
   - The denominator, \( 2\sqrt{1 + x^3} \), is always positive as well, since \( \sqrt{1 + x^3} \) is the square root of a positive function.

   Thus, \( h'(x) = \frac{3x^2}{2\sqrt{1 + x^3}} > 0 \) for all \( x \ge 1 \).

3. **Conclusion:**

   Since \( h'(x) > 0 \) for all \( x \) in the domain \([1, \infty)\), the function \( h(x) = \sqrt{1 + x^3} \) is always increasing on this interval.
Transcribed Image Text:**Problem Statement:** Show analytically (that is, without reference to a graph) that \( h(x) = \sqrt{1 + x^3} \) is always increasing, given that \( \text{Dom } h = [1, \infty) \). --- To demonstrate that the function \( h(x) \) is always increasing, you'll need to analyze its derivative \( h'(x) \). A function is increasing on an interval if its derivative is positive for all values in that interval. 1. **Differentiate \( h(x) \):** Apply the chain rule: \[ h(x) = (1 + x^3)^{1/2} \] \[ h'(x) = \frac{1}{2}(1 + x^3)^{-1/2} \cdot 3x^2 = \frac{3x^2}{2\sqrt{1 + x^3}} \] 2. **Analyze the derivative \( h'(x) \):** For the domain \( x \in [1, \infty) \): - The numerator, \( 3x^2 \), is always positive since \( x^2 \ge 0 \) and multiplying by 3 keeps it positive over the domain. - The denominator, \( 2\sqrt{1 + x^3} \), is always positive as well, since \( \sqrt{1 + x^3} \) is the square root of a positive function. Thus, \( h'(x) = \frac{3x^2}{2\sqrt{1 + x^3}} > 0 \) for all \( x \ge 1 \). 3. **Conclusion:** Since \( h'(x) > 0 \) for all \( x \) in the domain \([1, \infty)\), the function \( h(x) = \sqrt{1 + x^3} \) is always increasing on this interval.
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