Question 338737
{{{x^2 + y^2 = 25}}} is a relation, but not a function.
It's not a function because there is not a 1 to 1 relationship of values.
ie, you can sub +1 and -1 for x (or y) and find the same value for the other variable.
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To graph, dl the FREE software at http://www.padowan.dk.com
Use F6 to enter a relationship.