Math Problem Statement
For the polynomial function g, the rate of change of g is increasing for x<2 and decreasing for x>2. which of the following must be true?
1, the graph of g has a minimum at x=2 2. the graph of g has a maximum of x=2 3. the graph of g has a point of inflection at x=2, is concave down for x<2, and is concave up for x>2 4. the graph of g has a point of inflection at x=2, is concave up for x<2, and is concave down for x>2
Solution
The key here is the description of the behavior of the rate of change of the function . The rate of change of a function is its first derivative, . If the rate of change is increasing for and decreasing for , it suggests that the second derivative, , changes signs at .
To break it down:
- For : The rate of change is increasing, meaning is increasing, which implies . This indicates the graph is concave up.
- For : The rate of change is decreasing, meaning is decreasing, which implies . This indicates the graph is concave down.
- At : Since the concavity changes from positive (concave up) to negative (concave down), there is a point of inflection at .
Now, analyzing the given options:
-
The graph of has a minimum at :
- This is not necessarily true because the behavior of the first derivative does not indicate a minimum at , only a change in concavity.
-
The graph of has a maximum at :
- This is also not necessarily true for the same reason as above. We don’t have information about the first derivative behavior suggesting a maximum.
-
The graph of has a point of inflection at , is concave down for , and is concave up for :
- This is incorrect because for , the rate of change is increasing, implying concave up behavior, not concave down.
-
The graph of has a point of inflection at , is concave up for , and is concave down for :
- This is correct. The behavior of the second derivative changes from positive to negative, indicating a point of inflection at , with the concavity being up for and down for .
Conclusion:
The correct answer is Option 4.
Would you like more details on any specific part of this explanation?
Related questions:
- How can we use the second derivative test to confirm a maximum or minimum?
- What is the significance of a point of inflection in a function's graph?
- How does concavity affect the shape of a graph?
- What is the relationship between the second derivative and the concavity of a function?
- How can you determine intervals of concavity for a polynomial function?
Tip: Always remember, a point of inflection occurs where the concavity of the graph changes, which is where the second derivative changes sign.
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Math Problem Analysis
Mathematical Concepts
Calculus
Derivatives
Concavity
Points of Inflection
Formulas
First derivative: g'(x)
Second derivative: g''(x)
Theorems
Inflection point: A point where the concavity of the function changes.
Concavity: g''(x) > 0 for concave up, g''(x) < 0 for concave down.
Suitable Grade Level
Grades 11-12 (Pre-Calculus or Calculus)