Find an equation of the normal line to the parabola y = x² - 8x + 4 that is parallel to the line x - 4y = 4. y =

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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**Problem Statement:**

Find an equation of the normal line to the parabola \( y = x^2 - 8x + 4 \) that is parallel to the line \( x - 4y = 4 \).

**Solution:**

- **Step 1:** Determine the slope of the given line.
  - Rewrite \( x - 4y = 4 \) in slope-intercept form: 
    \[
    4y = x - 4 \quad \Rightarrow \quad y = \frac{1}{4}x - 1
    \]
  - The slope of the line is \( \frac{1}{4} \).

- **Step 2:** Find the derivative of the parabola to get the slope of the tangent line at any point \( (x, y) \). The derivative of \( y = x^2 - 8x + 4 \) is:
  \[
  \frac{dy}{dx} = 2x - 8
  \]

- **Step 3:** For the normal line to be parallel to \( x - 4y = 4 \), it must have the same slope as \( \frac{1}{4} \). Since the normal line is perpendicular to the tangent line at the point of tangency, the product of their slopes must be \(-1\):
  \[
  m_{\text{tangent}} \times \frac{1}{4} = -1 \quad \Rightarrow \quad m_{\text{tangent}} = -4
  \]

- **Step 4:** Set the slope of the tangent line \( 2x - 8 \) equal to \(-4\):
  \[
  2x - 8 = -4 \quad \Rightarrow \quad 2x = 4 \quad \Rightarrow \quad x = 2
  \]

- **Step 5:** Substitute \( x = 2 \) back into the equation of the parabola to find the \( y \)-coordinate:
  \[
  y = (2)^2 - 8(2) + 4 = 4 - 16 + 4 = -8
  \]
  The point of tangency is \( (2, -8) \).

- **Step 6:** Use the point-slope form to find the equation of the
Transcribed Image Text:**Problem Statement:** Find an equation of the normal line to the parabola \( y = x^2 - 8x + 4 \) that is parallel to the line \( x - 4y = 4 \). **Solution:** - **Step 1:** Determine the slope of the given line. - Rewrite \( x - 4y = 4 \) in slope-intercept form: \[ 4y = x - 4 \quad \Rightarrow \quad y = \frac{1}{4}x - 1 \] - The slope of the line is \( \frac{1}{4} \). - **Step 2:** Find the derivative of the parabola to get the slope of the tangent line at any point \( (x, y) \). The derivative of \( y = x^2 - 8x + 4 \) is: \[ \frac{dy}{dx} = 2x - 8 \] - **Step 3:** For the normal line to be parallel to \( x - 4y = 4 \), it must have the same slope as \( \frac{1}{4} \). Since the normal line is perpendicular to the tangent line at the point of tangency, the product of their slopes must be \(-1\): \[ m_{\text{tangent}} \times \frac{1}{4} = -1 \quad \Rightarrow \quad m_{\text{tangent}} = -4 \] - **Step 4:** Set the slope of the tangent line \( 2x - 8 \) equal to \(-4\): \[ 2x - 8 = -4 \quad \Rightarrow \quad 2x = 4 \quad \Rightarrow \quad x = 2 \] - **Step 5:** Substitute \( x = 2 \) back into the equation of the parabola to find the \( y \)-coordinate: \[ y = (2)^2 - 8(2) + 4 = 4 - 16 + 4 = -8 \] The point of tangency is \( (2, -8) \). - **Step 6:** Use the point-slope form to find the equation of the
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