This is my notes but not of my own.

# Functions

• Relation: A set of ordered pairs. `{(x1,y1), (x2,y2)}` such that `{}` is a relation.
• Domain: The set consisting of the first components of each ordered pair is called the domain. `{(x,y)}` such that `x` is a domain.
• Range: The set consisting of the second components of each ordered pair is called the range. `{ (x,y) }` such that `y` is a range.
• Input value (Independent variable): Each value in the domain is also known as an input value, or independent variable, and is often labeled with the lowercase letter `x` . The input values make up the domain.
• Output value( Dependent variable): Each value in the range is also known as an output value, or dependent variable, and is often labeled lowercase letter `y`. The output values make up the range.
• Function: A function `f` is a relation that assigns a single element in the range to each element in the domain. In other words, no x-values are repeated. A function is a relation in which each possible input value leads to exactly one output value. We say “the output is a function of the input.”

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