You can put this solution on YOUR website! Functions are described in terms of their domain and range.
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The domain is all the 'x' values for which the value of the function is defined.
Dividing by zero is undefined, so if 'x' is in the denominator of a fraction, then there likely is one or more places that the function value is undefined.
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The range is all the 'y' values.
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Functions are described in terms of their domain (the 'x' values) and the range (the 'y' values).
A graph can be helpful in determining the domain and range.