Unit 1: Limits and continuity, form the foundation of all Calculus. In Unit 1 you will learn how functions behave as inputs approach a value, how to determine whether limits exist, and how continuity connects algebra, graphs, and real‑world behavior.
Every major idea in calculus — derivatives, integrals, and series — relies on limits. Mastering this unit is essential for success throughout the AP Calculus course and on the AP exam.
Interpret limit notation and one‑sided limits graphically, numerically, and algebraically
Apply limit laws to evaluate limits efficiently
Use algebraic techniques such as factoring, conjugates, and common denominators when direct substitution fails
Identify when limits do not exist due to jumps, infinite behavior, or oscillation
Analyze infinite limits and determine vertical and horizontal asymptotes
Understand continuity and classify different types of discontinuities
Apply the Intermediate Value Theorem and properly justify conclusions
To succeed in this unit, you should:
Pay close attention to notation and definitions
Never assume continuity unless it is stated or justified
Clearly distinguish between a limit value and a function value
Practice explaining why conclusions are true, not just computing answers
Strong fundamentals here make the rest of AP Calculus far more manageable.
A limit describes what a function is approaching as x gets close to a value, not what the function equals at that point. The function value may exist even when the limit does not — and vice versa. Mixing these up is one of the most common mistakes in Unit 1.
A limit does not exist if:
The left‑hand and right‑hand limits are different
The function goes to positive or negative infinity
The function oscillates as x approaches a value
If any of these occur, the limit fails — even if the function is defined.
No. Always try direct substitution first. If substitution gives a real number, that is the limit. Algebraic techniques like factoring or conjugates are only needed when substitution results in 0/0.
Factoring: when you see rational functions.
Conjugates: when radicals cause 0/0.
Common denominators: when working with complex fractions.
There’s no guessing — the structure of the expression tells you the method.
No. On the AP exam, you must justify continuity before using the Intermediate Value Theorem. Even familiar functions must be stated as continuous on the given interval to earn full credit.
Limits at infinity describe long‑term behavior of a function. These limits help identify horizontal asymptotes, which frequently appear on multiple‑choice questions and graph interpretation problems.
Students often:
Assume continuity without stating it
Confuse a limit with a function value
Use correct math but incorrect notation
In Unit 1, how you explain/justify matters just as much as what you compute.