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 gg. The rate of change of a function is its first derivative, g(x)g'(x). If the rate of change is increasing for x<2x < 2 and decreasing for x>2x > 2, it suggests that the second derivative, g(x)g''(x), changes signs at x=2x = 2.

To break it down:

  • For x<2x < 2: The rate of change is increasing, meaning g(x)g'(x) is increasing, which implies g(x)>0g''(x) > 0. This indicates the graph is concave up.
  • For x>2x > 2: The rate of change is decreasing, meaning g(x)g'(x) is decreasing, which implies g(x)<0g''(x) < 0. This indicates the graph is concave down.
  • At x=2x = 2: Since the concavity changes from positive (concave up) to negative (concave down), there is a point of inflection at x=2x = 2.

Now, analyzing the given options:

  1. The graph of gg has a minimum at x=2x = 2:

    • This is not necessarily true because the behavior of the first derivative does not indicate a minimum at x=2x = 2, only a change in concavity.
  2. The graph of gg has a maximum at x=2x = 2:

    • 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.
  3. The graph of gg has a point of inflection at x=2x = 2, is concave down for x<2x < 2, and is concave up for x>2x > 2:

    • This is incorrect because for x<2x < 2, the rate of change is increasing, implying concave up behavior, not concave down.
  4. The graph of gg has a point of inflection at x=2x = 2, is concave up for x<2x < 2, and is concave down for x>2x > 2:

    • This is correct. The behavior of the second derivative changes from positive to negative, indicating a point of inflection at x=2x = 2, with the concavity being up for x<2x < 2 and down for x>2x > 2.

Conclusion:

The correct answer is Option 4.

Would you like more details on any specific part of this explanation?


Related questions:

  1. How can we use the second derivative test to confirm a maximum or minimum?
  2. What is the significance of a point of inflection in a function's graph?
  3. How does concavity affect the shape of a graph?
  4. What is the relationship between the second derivative and the concavity of a function?
  5. 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)