If the radius of the sphere S is 8 units, what is the value of k ?

For the next two (02) items that follow : The equation of the sphere S is \( x^2 + y^2 + z^2 - 4x - 6y - 12z + k = 0 \).

  1. A. -15
  2. B. 7
  3. C. 10
  4. D. 15

Correct Answer: A. -15

Explanation

The radius r of a sphere is given by \sqrt{u^2 + v^2 + w^2 - d}. Here, \sqrt{2^2 + 3^2 + 6^2 - k} = 8. So, 49 - k = 64, which gives k = -15.

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