Question 674461
Determine whether the equation is a function. 
x^2-4y^2=1
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It is not a function because there are 2 y-values for each 
x value.
4y^2 = x^2-1
y^2 = (x^2-1)/4
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y = +Sqrt[(x^2-1)/4] AND = -sqrt[(x^2-1)/4]
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Cheers,
Stan H.
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