Function Notation f(x)

Algebra 1 · Axiom Academy

EXAMPLE Introduction to Function Notation Evaluate a function by substituting values for the variable in its rule. Given the function f(x) = 2x + 3 , evaluate it at three different inputs: f(5) , f(-2) , and f(a+1) . Nice work — you have evaluated a function at three kinds of input. Here is what to carry forward: A function is a rule: f(x) = 2x + 3 takes an input (the x ) and returns one specific output. Substitution is everything: means "replace every x in the rule with whatever is in the parentheses." The input can be anything: a positive number f(5) = 13 , a negative number f(-2) = -1 , or a whole expression f(a+1) = 2a + 5 — the process never changes. Master substitution now and every later topic — composition, transformations, derivatives — becomes the same move on a more interesting rule.

This is the written version of the interactive lesson above. See the full Algebra 1 course.