Decreasing Intervals Practice: Function Analysis Problems

Master identifying decreasing intervals of functions with step-by-step practice problems. Learn where function values decrease as x increases through guided exercises.

📚What You'll Practice with Decreasing Intervals
  • Identify decreasing intervals where function values drop as x increases
  • Locate maximum points that begin decreasing intervals in graphs
  • Analyze function behavior using interval notation for decreasing sections
  • Distinguish between increasing and decreasing intervals on function graphs
  • Apply decreasing interval concepts to real-world function problems
  • Interpret function values and their relationship to x-value changes

Understanding Decreasing Interval of a function

Complete explanation with examples

The decreasing intervals of a function

A decreasing interval of a function expresses the same values of X (the interval), in which the values of the function (Y) decrease parallelly to the increase of the values of X to the right.

In certain cases, the decreasing interval begins at the maximum point, but it does not necessarily have to be this way.

Detailed explanation

Practice Decreasing Interval of a function

Test your knowledge with 17 quizzes

Determine the domain of the following function:

The function describes a student's grades throughout the year.

Examples with solutions for Decreasing Interval of a function

Step-by-step solutions included
Exercise #1

Does the function in the graph decrease throughout?

YYYXXX

Step-by-Step Solution

To solve this problem, we'll begin by examining the graph of the function provided:

  • Step 1: Observe the graph from left to right along the x-axis.
  • Step 2: Look for any intervals where the function value (y-coordinate) does not decrease as the x-value increases.
  • Step 3: Pay special attention to segments where the graph might look horizontal or rising.

Upon inspecting the graph, we find:

- There are sections where the function's y-values appear to remain constant or potentially rise as the x-values increase. Specifically, even if the function decreases in major portions, any interval where it doesn't means the function cannot be classified as decreasing throughout.

Thus, the function does not strictly decrease on the entire interval shown. Therefore, the solution to the problem is No.

Answer:

No

Exercise #2

Is the function in the graph below decreasing?

yx

Step-by-Step Solution

To determine if the function is decreasing, we will analyze the graph visually:

The graph shows a line connecting from the bottom-left to the top-right of the graph area, indicating the line has a positive slope. This type of graph indicates the function is increasing, not decreasing.

A decreasing function means its value goes down as x x increases, which is equivalent to having a negative slope.

Since the graph appears with a positive slope, the function is not decreasing.

Thus, the correct choice to the problem, which asks if the function in the graph is decreasing, is No.

Answer:

No

Exercise #3

Is the function in the graph decreasing?

yx

Step-by-Step Solution

To analyze whether the function in the graph is decreasing, we must understand how the function's behavior is defined by its graph:

  • Step 1: Examine the graph. The graph presented is a horizontal line.
  • Step 2: Recognize the properties of a horizontal line. Horizontally aligned lines correspond to constant functions because the y y -value remains the same for all x x -values.
  • Step 3: Define the criteria for a function to be decreasing. A function decreases when, as x x increases, the value of f(x) f(x) decreases.
  • Step 4: Apply this criterion to the horizontal line. Since the y y -value is constant and does not decrease as x x moves rightward, the function is not decreasing.

Therefore, the function represented by the graph is not decreasing.

Answer:

No

Exercise #4

Is the function in the graph decreasing? yx

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Verify the graph's overall path direction
  • Step 2: Confirm if the y-values are decreasing as we proceed from the left side of the graph to the right side (increasing x-values).

Now, let's work through each step:

Step 1: By examining the graph, the red line starts at a higher point on the y-axis and moves downward to a lower point as it moves horizontally across the x-axis from left to right.

Step 2: Since for every point, the red line descends as it progresses from the leftmost point to the rightmost, this indicates a consistent decrease in the y-values.

Therefore, the solution to the problem is Yes, the function in the graph is decreasing.

Answer:

Yes

Exercise #5

Is the function shown in the graph below decreasing?

yx

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Visually inspect the graph to see if it is consistently sloping downward.
  • Step 2: Apply the definition of a decreasing function.

Now, let's work through each step:
Step 1: Observing the graph, the function's graph is a line moving from the top left to the bottom right. This indicates it slopes downward as we move from left to right across the x x -axis.
Step 2: According to the definition of a decreasing function, for any x1<x2 x_1 < x_2 , it must hold true that f(x1)>f(x2) f(x_1) > f(x_2) . Since the graph shows a line moving downward, this condition is satisfied throughout its domain.

Therefore, the function represented by the graph is indeed decreasing.

The final answer is Yes.

Answer:

Yes

Frequently Asked Questions

What is a decreasing interval of a function?

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A decreasing interval is a range of x-values where the function values (y-values) get smaller as x increases from left to right. On a graph, this appears as a downward slope moving from left to right.

How do you find decreasing intervals on a graph?

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Look for sections where the graph slopes downward from left to right. These are the decreasing intervals. You can identify them by checking: 1) Find where the graph goes down, 2) Note the x-values at the start and end, 3) Write the interval using proper notation.

Do decreasing intervals always start at maximum points?

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No, decreasing intervals don't always begin at maximum points. While they often start after a peak (maximum), they can also begin at the start of the function's domain or after other types of critical points.

What's the difference between increasing and decreasing intervals?

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Increasing intervals show function values rising as x increases (upward slope), while decreasing intervals show function values falling as x increases (downward slope). They represent opposite behaviors of the function.

How do you write decreasing intervals in interval notation?

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Use parentheses or brackets to show the x-values where the function decreases. For example, if a function decreases from x = 2 to x = 5, write it as (2, 5) or [2, 5] depending on whether the endpoints are included.

Can a function have multiple decreasing intervals?

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Yes, functions can have multiple decreasing intervals separated by increasing sections or constant regions. Each separate downward-sloping section represents a distinct decreasing interval that should be identified separately.

Why are decreasing intervals important in math?

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Decreasing intervals help analyze function behavior, predict trends, and solve optimization problems. They're essential for understanding rates of change, finding minimum values, and modeling real-world situations like declining populations or decreasing temperatures.

What are common mistakes when identifying decreasing intervals?

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Common errors include: confusing x-intervals with y-values, mixing up increasing and decreasing directions, forgetting to use proper interval notation, and not recognizing that steep downward slopes are still decreasing intervals regardless of steepness.

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