8. Find the equation of the horizontal tangent line to the curve y = -x + yx.

Calculus: Early Transcendentals
8th Edition
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Author:James Stewart
Publisher:James Stewart
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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**Question 8:** Find the equation of the horizontal tangent line to the curve \( y = -x + \sqrt{x} \).

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*Explanation:*

To solve this problem, we would first take the derivative of the function \( y = -x + \sqrt{x} \) with respect to \( x \) to find the slope of the tangent line at any point \( x \) on the curve. Next, we set the derivative equal to zero to find the point(s) at which the tangent line is horizontal.

1. Start by differentiating the function \( y \):

\[ \frac{dy}{dx} = \frac{d}{dx} \left(-x + \sqrt{x} \right) \]

2. Use the power rule to differentiate the individual terms within the function:

\[ \frac{dy}{dx} = -1 + \frac{1}{2}x^{-1/2} \]

3. Simplify the derivative:

\[ \frac{dy}{dx} = -1 + \frac{1}{2\sqrt{x}} \]

4. Set the derivative equal to zero to find the point(s) where the tangent line is horizontal:

\[ -1 + \frac{1}{2\sqrt{x}} = 0 \]

5. Solve for \( x \):

\[ \frac{1}{2\sqrt{x}} = 1 \]
\[ \frac{1}{2\sqrt{x}} = 1 \]
\[ \sqrt{x} = \frac{1}{2} \]
\[ x = \left( \frac{1}{2} \right)^2 \]
\[ x = \frac{1}{4} \]

6. Substitute \( x = \frac{1}{4} \) back into the original equation to find \( y \):

\[ y = -\left( \frac{1}{4} \right) + \sqrt{ \frac{1}{4} } \]
\[ y = -\frac{1}{4} + \frac{1}{2} \]
\[ y = \frac{1}{4} \]

Therefore, the horizontal tangent line occurs at the point \( \left( \frac{1}{4}, \frac{1}{4} \right) \). The equation of the horizontal tangent line is:

\[ y = \frac{1}{4} \]

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In summary, for the curve
Transcribed Image Text:**Question 8:** Find the equation of the horizontal tangent line to the curve \( y = -x + \sqrt{x} \). --- *Explanation:* To solve this problem, we would first take the derivative of the function \( y = -x + \sqrt{x} \) with respect to \( x \) to find the slope of the tangent line at any point \( x \) on the curve. Next, we set the derivative equal to zero to find the point(s) at which the tangent line is horizontal. 1. Start by differentiating the function \( y \): \[ \frac{dy}{dx} = \frac{d}{dx} \left(-x + \sqrt{x} \right) \] 2. Use the power rule to differentiate the individual terms within the function: \[ \frac{dy}{dx} = -1 + \frac{1}{2}x^{-1/2} \] 3. Simplify the derivative: \[ \frac{dy}{dx} = -1 + \frac{1}{2\sqrt{x}} \] 4. Set the derivative equal to zero to find the point(s) where the tangent line is horizontal: \[ -1 + \frac{1}{2\sqrt{x}} = 0 \] 5. Solve for \( x \): \[ \frac{1}{2\sqrt{x}} = 1 \] \[ \frac{1}{2\sqrt{x}} = 1 \] \[ \sqrt{x} = \frac{1}{2} \] \[ x = \left( \frac{1}{2} \right)^2 \] \[ x = \frac{1}{4} \] 6. Substitute \( x = \frac{1}{4} \) back into the original equation to find \( y \): \[ y = -\left( \frac{1}{4} \right) + \sqrt{ \frac{1}{4} } \] \[ y = -\frac{1}{4} + \frac{1}{2} \] \[ y = \frac{1}{4} \] Therefore, the horizontal tangent line occurs at the point \( \left( \frac{1}{4}, \frac{1}{4} \right) \). The equation of the horizontal tangent line is: \[ y = \frac{1}{4} \] --- In summary, for the curve
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