What is the radius of a circle if its equation is x^2 + y^2 = 9? (
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What is the value of f(x) when f(x) = c, a constant value?
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What is the equation of a hyperbola if its vertices are located at (-3,0) and (3,0), its foci are located at (-5,0) and (5,0), and the length of its conjugate axis is 4?