Math Problem Statement

Consider the function f(x), defined for x ≥ 0. The following information is given: f(0) = 2, f(x) has negative first derivatives and positive second derivatives for 0 ≤ x < 3, f(3) = -2 with both first and second derivatives at zero, and f(x) has negative first and second derivatives for x > 3. Answer the following: a. The graph of y = f(x) has a stationary point of inflection. What are the coordinates of this stationary point of inflection? b. Select the correct answer for the following: For 0 ≤ x < 3, the shape of the curve of y = f(x) is concave upwards (convex) or concave downwards. c. Sketch a continuous smooth curve of the graph of y = f(x) for x ≥ 0, using the given information and your answers to parts a and b.

Solution

Let's go through each part of this problem step-by-step.

Given Information

We are given:

  • A function f(x)f(x) defined for x0x \geq 0.
  • A table with values of f(x)f(x), f(x)f'(x), and f(x)f''(x) for various intervals of xx:
    • At x=0x = 0: f(x)=2f(x) = 2
    • For 0x<30 \leq x < 3: f(x)<0f'(x) < 0 and f(x)>0f''(x) > 0
    • At x=3x = 3: f(x)=2f(x) = -2, f(x)=0f'(x) = 0, and f(x)=0f''(x) = 0
    • For x>3x > 3: f(x)<0f'(x) < 0 and f(x)<0f''(x) < 0

Using this, we can answer the questions.

Part (a)

The problem states that the graph of y=f(x)y = f(x) has a stationary point of inflection.

A stationary point of inflection is a point where:

  1. The derivative f(x)=0f'(x) = 0.
  2. The second derivative f(x)f''(x) changes sign (indicating a change in concavity).

From the table, we see that at x=3x = 3:

  • f(3)=0f'(3) = 0, so it's a stationary point.
  • f(3)=0f''(3) = 0, and the concavity changes from f(x)>0f''(x) > 0 for x<3x < 3 to f(x)<0f''(x) < 0 for x>3x > 3.

Thus, x=3x = 3 is a stationary point of inflection.

Answer for Part (a): The coordinates of the stationary point of inflection are (3,2)(3, -2).

Part (b)

For 0x<30 \leq x < 3, we are asked about the concavity of y=f(x)y = f(x).

From the table, we know:

  • For 0x<30 \leq x < 3: f(x)>0f''(x) > 0, which means the curve is concave upwards (or convex) on this interval.

Answer for Part (b): The correct answer is concave upwards (convex).

Part (c)

We need to sketch a continuous smooth curve for y=f(x)y = f(x) for x0x \geq 0, using the information from parts (a) and (b).

Here's the process:

  1. At x=0x = 0: The value of f(x)f(x) is 22.
  2. From 0x<30 \leq x < 3: f(x)f(x) is decreasing (since f(x)<0f'(x) < 0) and concave upwards (since f(x)>0f''(x) > 0).
  3. At x=3x = 3: The function reaches f(x)=2f(x) = -2, and there is a stationary point of inflection here, where the graph changes from concave upwards to concave downwards.
  4. For x>3x > 3: f(x)f(x) continues to decrease (since f(x)<0f'(x) < 0) and is concave downwards (since f(x)<0f''(x) < 0).

In your sketch:

  • Start at (0,2)(0, 2).
  • Draw a decreasing, concave-up curve toward (3,2)(3, -2).
  • At x=3x = 3, have the curve inflect and switch to concave downwards, continuing to decrease for x>3x > 3.

Would you like more details on any part of the solution? Here are five additional questions for practice:

  1. What defines a stationary point in calculus?
  2. How do we identify an inflection point on a graph?
  3. Why does f(x)f(x) have to be concave upwards for 0x<30 \leq x < 3?
  4. What is the significance of the concavity change at x=3x = 3?
  5. How does the behavior of f(x)f(x) for x>3x > 3 influence the overall shape of the graph?

Tip: Remember, a stationary point of inflection requires both the first and second derivatives to be zero at that point, and a change in concavity around the point.

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Math Problem Analysis

Mathematical Concepts

Calculus
Differentiation
Stationary Points
Inflection Points
Concavity

Formulas

f'(x) = 0 at stationary points
f''(x) changes sign at inflection points

Theorems

Stationary point of inflection definition

Suitable Grade Level

Grades 10-12