Functions & Function Notation
Section: AlgebraBank code: ALG-FNCGRE frequency: HighPro
1. Core Idea
A function is a rule that assigns exactly one output to each input. f(x) is not multiplication — it means "the output of f when the input is x".
The single most useful mental model: f is a machine, and x is whatever you feed it. Whatever appears inside the brackets replaces every x in the rule.
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