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Relationships can be any association between sets of numbers while functions have only one output for a given input. This tutorial works through a bunch of examples of testing whether something is a valid function. As always, we really encourage you to pause the videos and try the problems before Sal does!
Functions assign a single unique output for each of their inputs. In this video, Sal gives many examples of various kinds of functions.
Jesse Roe and Sal talk about the difference between equations and functions
Relations and Functions
Linear Function Graphs
Sal evaluates f(x)=49-x^2 at x=5.
Sal evaluates a function at x=-1 using the graph of that function.
Evaluate functions at a specific input value, given either the functions' formula or their graph.