MathematicsLocal extreme valuesUniversity
IBUndergraduate

Decreasing function

Defines a decreasing function as one whose outputs fall as inputs increase on an interval.

Understand the formulaSee the free derivationOpen the full walkthrough
Open Full WalkthroughTry Calculator

This public page keeps the free explanation visible and leaves premium worked solving, advanced walkthroughs, and saved study tools inside the app.

Core idea

Overview

Defines a decreasing function as one whose outputs fall as inputs increase on an interval. It explains the calculus condition behind the rule and how that condition controls graph behavior. Students should use it to decide what can be concluded from derivatives, extrema, or interval hypotheses.

When to use: Use this when a calculus problem asks about monotonicity, concavity, local extrema, mean-value-theorem consequences, or indeterminate quotient forms.

Why it matters: These tests turn derivative information into clear statements about graph behavior and limits.

Symbols

Variables

result = result

result
result
Variable

Walkthrough

Derivation

Derivation of Decreasing function

Defines a decreasing function as one whose outputs fall as inputs increase on an interval.

  • and are in the interval I.
  • The comparison uses <.
1

State the verified result

This is the standard calculus statement used for this entry.

2

Use the hypotheses

The conclusion is valid only under the stated assumptions.

Result

Source: OpenStax, Calculus Volume 1, Section 4.5: Derivatives and the Shape of a Graph, accessed 2026-04-09

Free formulas

Rearrangements

Solve for

Use Decreasing function

Check the hypotheses, then apply the definition or derivative test exactly as stated.

Difficulty: 2/5

The static page shows the finished rearrangements. The app keeps the full worked algebra walkthrough.

Why it behaves this way

Intuition

Read the graph from left to right: derivative signs describe rising or falling, second derivative signs describe bending, and indeterminate forms warn that a limit cannot be read from substitution alone.

function
The rule whose values or derivatives are being studied.
interval
The set over which behavior is being claimed.
f'
first derivative
Slope or instantaneous rate of change.

Signs and relationships

  • =>: The hypotheses imply the conclusion; the implication is not automatically reversible.

One free problem

Practice Problem

Is f(x)=-x decreasing on all real numbers?

out0

Solve for: result

Hint: Check the definition, derivative sign, or limit form before concluding.

The full worked solution stays in the interactive walkthrough.

Where it shows up

Real-World Context

Motion, cost, and growth models use derivative signs to identify whether quantities are rising, falling, leveling, or bending.

Study smarter

Tips

  • Check the interval first.
  • Check all hypotheses before using the conclusion.
  • Do not treat a theorem statement as a numeric calculator.

Avoid these traps

Common Mistakes

  • Skipping a required continuity or differentiability condition.
  • Using a one-point derivative value to conclude behavior on a whole interval.

Common questions

Frequently Asked Questions

Defines a decreasing function as one whose outputs fall as inputs increase on an interval.

Use this when a calculus problem asks about monotonicity, concavity, local extrema, mean-value-theorem consequences, or indeterminate quotient forms.

These tests turn derivative information into clear statements about graph behavior and limits.

Skipping a required continuity or differentiability condition. Using a one-point derivative value to conclude behavior on a whole interval.

Motion, cost, and growth models use derivative signs to identify whether quantities are rising, falling, leveling, or bending.

Check the interval first. Check all hypotheses before using the conclusion. Do not treat a theorem statement as a numeric calculator.

References

Sources

  1. OpenStax, Calculus Volume 1, Section 4.5: Derivatives and the Shape of a Graph, accessed 2026-04-09
  2. Wikipedia: Monotonic function, accessed 2026-04-09
  3. IUPAC Gold Book
  4. Wikipedia: Decreasing function