Understand function notation f(x), evaluate functions at given values, and interpret function language.
A function is a rule that takes an input and produces exactly one output. Think of it as a machine: - You feed in a number (input x) - The machine applies a rule - Out comes exactly one result (output y) We write f(x) (read "f of x") to mean "the output of function f when the input is x." Important: f(x) does NOT mean f times x. The parentheses here mean "function of," not multiplication.
To evaluate f(a), replace every x in the formula with a. This is the single most important skill for function questions on the SAT.
Example: If f(x) = 3x + 7, find f(4).
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