Chapter 2: Problem 38
The graph of each function has one relative extreme point. Find it (giving both \(x\) - and \(y\) -coordinates) and determine if it is a relative maximum or a relative minimum point. Do not include a sketch of the graph of the function. $$ g(x)=x^{2}+10 x+10 $$
Short Answer
Expert verified
The relative minimum point is at \( (-5, -15) \).
Step by step solution
01
- Find the first derivative
To find the relative extreme point of the function, first compute the derivative of the function. For the function \( g(x) = x^2 + 10x + 10 \), the first derivative is \( g'(x) \). Differentiate each term separately:\[ g'(x) = \frac{d}{dx}(x^2) + \frac{d}{dx}(10x) + \frac{d}{dx}(10) \]Applying the power rule and constant rule:\[ g'(x) = 2x + 10 \]
02
- Set the first derivative to zero
Set the derivative equal to zero and solve for \( x \):\[ 2x + 10 = 0 \]Subtract 10 from both sides:\[ 2x = -10 \]Divide both sides by 2:\[ x = -5 \]
03
- Find the second derivative
To determine if the critical point is a maximum or minimum, find the second derivative of the function. For the function \( g(x) = x^2 + 10x + 10 \), differentiate the first derivative \( g'(x) = 2x + 10 \):\[ g''(x) = \frac{d}{dx}(2x + 10) = 2 \]
04
- Analyze the second derivative
Evaluate the second derivative. Since \( g''(x) = 2 \), which is greater than 0, the critical point at \( x = -5 \) is a relative minimum.
05
- Calculate the y-coordinate
Substitute \( x = -5 \) back into the original function to find the corresponding \( y \)-coordinate:\[ g(-5) = (-5)^2 + 10(-5) + 10 \]Simplify:\[ g(-5) = 25 - 50 + 10 = -15 \]So the coordinates of the relative minimum point are \( (-5, -15) \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
First Derivative
The first derivative of a function, often denoted as \( f'(x) \), provides crucial information about the function's rate of change. For a given function \( g(x) = x^2 + 10x + 10 \), the first derivative is found by differentiating each term: \( g'(x) = 2x + 10 \). This tells us how the function's output changes as the input \( x \) changes.
To compute the first derivative:
To compute the first derivative:
- Apply the power rule to \( x^2 \), which gives \( 2x \).
- The derivative of \( 10x \) is \( 10 \).
- Since the derivative of a constant is zero, \( \frac{d}{dx}(10) = 0 \).
- Summarize to obtain \( g'(x) = 2x + 10 \).
Critical Points
Critical points of a function occur where its first derivative is zero or undefined. These points are potential locations of relative extrema (maximum or minimum). For \( g(x) = x^2 + 10x + 10 \), we first find its first derivative to be \( g'(x) = 2x + 10 \). Setting \( g'(x) = 0 \) to find the critical points provides:
- \( 2x + 10 = 0 \)
- Solve for \( x \): \( 2x = -10 \)
- \( x = -5 \)
Second Derivative Test
The second derivative test determines the concavity of the function and thus identifies whether a critical point is a relative maximum or minimum. For \( g(x) = x^2 + 10x + 10 \), we first found \( g'(x) = 2x + 10 \). Now, we find the second derivative \( g''(x) \):
The second derivative test can be summarized as:
- Differentiate \( g'(x) = 2x + 10 \), which gives \( g''(x) = 2 \).
The second derivative test can be summarized as:
- If \( g''(x) > 0 \), the function has a relative minimum at the critical point.
- If \( g''(x) < 0 \), the function has a relative maximum at the critical point.
Relative Extrema
Relative extrema are the points where the function reaches a local maximum or minimum. Using the critical points and the second derivative test, we determine the nature of these extrema. For the given function \( g(x) = x^2 + 10x + 10 \) with the critical point \( x = -5 \):
- We substitute \( x = -5 \) back into the original function to find the \( y \)-coordinate: \( g(-5) = (-5)^2 + 10(-5) + 10 \).
- Simplify to get \( g(-5) = 25 - 50 + 10 = -15 \).