###### Alissa Fong

MA, Stanford University
Teaching in the San Francisco Bay Area

Alissa is currently a teacher in the San Francisco Bay Area and Brightstorm users love her clear, concise explanations of tough concepts

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Introduction to Functions - Problem 5

# Introduction to Functions - Problem 4

Alissa Fong
###### Alissa Fong

MA, Stanford University
Teaching in the San Francisco Bay Area

Alissa is currently a teacher in the San Francisco Bay Area and Brightstorm users love her clear, concise explanations of tough concepts

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A relation is any kind of mapping from a set of inputs to a set of outputs. A specific subset of relations are functions, where every input is mapped to exactly one output. From a map, make sure each input is matched to one output- it's OK if some outputs are used by multiple inputs. In a table, look to see that every x has only one y and that no x values repeat. In a graph, we use the vertical line test: if any vertical line you draw through a graph touches the graph in zero or one only place, then the graph represents a function relationship.

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