What are the characteristics of an ellipse given by the equation (x^2/a^2) + (y^2/b^2) = 1, where a represents the horizontal radius and b represents the vertical radius?
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What is the radius, r, of a circle if its equation is given by x^2 + y^2 = 9?
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What is the limit as x approaches 3 of (x^2 - 9) / (x - 3)