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Algebra I Recipe: Functions and Relations
A. Definitions
  1. Relation – a set of ordered pairs ie. {(1,2), (3,4), (5,6)}
  2. Domain – the x-values of the relation. (1,3,5)
  3. Range – the y-values of the relation. (2,4,6)
B. Identifying Relations that are Functions
  1. A relation is a function if no ordered pair has the same x-value.
  2. The graph of a relation is a function if a vertical line touches the graph at only one point, as the vertical line passes over the graph. (Vertical Line Test)
{(1,4), (2,3), (3,2), (4,1)}

{(-1,0), (7,-2), (2,4), (-1,-6)}

C. Evaluating a Function (that’s in equation form)
         **f(x) replaces y and is read "f of x"
  1. Substitute the given x-value in for x.
  2. Simplify by using order of operations.
Determine f(-2), that is, evaluate f(x) = 3x + 2 for x = -2
Determine f(-4), that is, evaluate f(x) = 2x² - 1 for x = -4

G Redden

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