What is the diameter of a circle with the equation (x – 4)2 + (y + 6)2 = 64?

A circle in standard form has equation (x − h)² + (y − k)² = r², so its radius is the square root of 64, which is 8. The diameter is twice the radius: 2 × 8 = 16, so the correct choice is 16.

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