What are the center and radius of the circle x^2 + y^2 - 6x + 2y - 15 = 0?
Answer and explanation
Correct answer: D. center (3, -1), radius 5
- Step 1: Complete the square in x and in y.
- Step 2: (x - 3)^2 + (y - -1)^2 = 25, so the center is (3, -1) and the radius is 5.
Answer
center (3, -1), radius 5.
Why not the others: The center has the opposite signs of the linear coefficients halved, and the right-hand side is the radius squared.
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