(e) dy if y = (t +1)(t + 9) %3D dt It%3D3

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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The problem presented is to find the derivative of \( y \) with respect to \( t \) evaluated at \( t = 3 \), where \( y = (t^2 + 1)(t + 9) \).

### Steps to Solve:

1. **Apply the Product Rule:**
   The function \( y \) is the product of two functions: \( u = t^2 + 1 \) and \( v = t + 9 \).
   The product rule states that the derivative of a product \( uv \) is given by:

   \[
   \frac{dy}{dt} = u'v + uv'
   \]

2. **Differentiate Each Function:**
   - \( u = t^2 + 1 \)  
     \( u' = \frac{du}{dt} = 2t \)

   - \( v = t + 9 \)  
     \( v' = \frac{dv}{dt} = 1 \)

3. **Substitute and Simplify:**
   Substitute \( u \), \( u' \), \( v \), and \( v' \) into the product rule:

   \[
   \frac{dy}{dt} = (2t)(t + 9) + (t^2 + 1)(1)
   \]

   \[
   \frac{dy}{dt} = 2t(t + 9) + (t^2 + 1)
   \]

   Simplify:

   \[
   2t(t + 9) = 2t^2 + 18t
   \]

   \[
   \frac{dy}{dt} = 2t^2 + 18t + t^2 + 1 = 3t^2 + 18t + 1
   \]

4. **Evaluate at \( t = 3 \):**

   \[
   \frac{dy}{dt}\bigg|_{t=3} = 3(3)^2 + 18(3) + 1
   \]

   \[
   = 3(9) + 54 + 1
   \]

   \[
   = 27 + 54 + 1 = 82
   \]

The value of \( \frac{dy}{dt} \) at \( t = 3 \) is
Transcribed Image Text:The problem presented is to find the derivative of \( y \) with respect to \( t \) evaluated at \( t = 3 \), where \( y = (t^2 + 1)(t + 9) \). ### Steps to Solve: 1. **Apply the Product Rule:** The function \( y \) is the product of two functions: \( u = t^2 + 1 \) and \( v = t + 9 \). The product rule states that the derivative of a product \( uv \) is given by: \[ \frac{dy}{dt} = u'v + uv' \] 2. **Differentiate Each Function:** - \( u = t^2 + 1 \) \( u' = \frac{du}{dt} = 2t \) - \( v = t + 9 \) \( v' = \frac{dv}{dt} = 1 \) 3. **Substitute and Simplify:** Substitute \( u \), \( u' \), \( v \), and \( v' \) into the product rule: \[ \frac{dy}{dt} = (2t)(t + 9) + (t^2 + 1)(1) \] \[ \frac{dy}{dt} = 2t(t + 9) + (t^2 + 1) \] Simplify: \[ 2t(t + 9) = 2t^2 + 18t \] \[ \frac{dy}{dt} = 2t^2 + 18t + t^2 + 1 = 3t^2 + 18t + 1 \] 4. **Evaluate at \( t = 3 \):** \[ \frac{dy}{dt}\bigg|_{t=3} = 3(3)^2 + 18(3) + 1 \] \[ = 3(9) + 54 + 1 \] \[ = 27 + 54 + 1 = 82 \] The value of \( \frac{dy}{dt} \) at \( t = 3 \) is
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