AP Calculus AB and BC glossary
Domain
The domain of a function is the set of inputs for which it produces a value. Domain restrictions determine where a function can be continuous or differentiable, and they are what make some answers to calculus problems invalid.
The usual restrictions are denominators that cannot be zero, square roots that need non-negative arguments, and logarithms that need strictly positive arguments. Each one creates a place where continuity must be checked.
Check the answer against it
Optimization and related rates problems often produce algebraically valid solutions that fall outside the domain, such as a negative length. Discarding those is part of the work.
Appears in: Unit 1: Limits and Continuity