Skip to content
Marlbridge

AP® Calculus AB · Unit 5 · Topic 5.3

Determining Intervals on Which a Function Is Increasing or Decreasing: Topic Checklist (Calculus AB 5.3)

Specific “I can…” statements for finding where a function increases or decreases, each linked to the guide section and practice question that tests it.

Work through the list without notes or a calculator. If you cannot do a statement, follow its link, then come back. Guide = study guide; Practice = practice questions. This topic is shared by Calculus AB and Calculus BC.

Understanding

  • I can state what it means for f to be increasing or decreasing on an interval, by comparing f(x₁) and f(x₂). (Guide: “What increasing and decreasing mean”)
  • I can explain, using the Mean Value Theorem, why f′(x) > 0 on an interval makes f increasing there. (Guide: “The link to the derivative”)
  • I can explain why a single zero of f′, with the same sign on both sides, does not end an interval of increase. (Guide: the x³ example; Practice Q2)
  • I can explain the difference between f′ being positive and f′ being increasing. (Guide: Worked example 2 “The trap”; Practice Q4, Q6(d))

Skills

  • I can differentiate, factor f′ and build a sign chart with test values or factor signs. (Guide: Worked example 1; Practice Q1, Q3)
  • I can include every split point: zeros of f′, points where f′ is undefined, and gaps in the domain of f. (Guide: “When the domain has a gap”; Practice Q7)
  • I can read the intervals where f increases or decreases from a graph of f′. (Guide: Worked example 2, Figure 1; Practice Q5)
  • I can find where a quantity is increasing in context from the sign of its rate, and give units. (Guide: “Increasing and decreasing in context”; Practice Q6)

Reasoning

  • I can write a justification that names f (or the quantity), the interval and the sign of f′. (Guide: “Writing a justification”; Practice Q5, Q6)
  • I can compare two values of f, such as f(3) and f(1), using an interval where f is increasing or decreasing. (Practice Q5(d), Q6(c))
  • I can explain why I must not join intervals across a point where f is undefined. (Guide: h(x) = x + 4/x)

All ticked? Move on to Topic 5.4, Using the First Derivative Test to Determine Relative (Local) Extrema, or return to the Calculus AB roadmap or the Calculus BC roadmap.

AP® and Advanced Placement® are trademarks registered by the College Board, which is not affiliated with, and does not endorse, this website. Marlbridge is an independent tuition provider. It is not an authorized AP course provider, an AP school or an exam centre, and these resources are not official College Board materials. Reading them or doing simulations does not meet the laboratory requirement of an AP science course.