Question

A point moves such that the sum of its distances from points (4, 0, 0) and (–4, 0, 0) is always equal to 10. Its locus is

• A. 9x² + 25y² – 25z² + 225 = 0
• B. 9x² + 25y² + 25z² – 225 = 0
• C. 9x² + 25y² + 25z² + 225 = 0
• D. None of these

Answer 1

Answer: (B)

9x² + 25y² + 25z² – 225 = 0

Answer 2

$\sqrt{(x - 4)^{2} + y^{2} + z^{2}} + \sqrt{(x + 4)^{2} + y^{2} + z^{2}} = 10$

Solve yourself.