Question

Find an equation of the sphere with points P such that the distance from P to A(−3, 4, 4) is twice the distance from P to B(6, 3, −1). Find its center and radius. center (x, y, z) = radius

Answer 1

Therefore, we conclude that the center of sphere at point

(27/3, -8/3, -8/3) with a radius 6.89.

Explanation:

We have the formula for distance, we get

\sqrt{(x+3)^2+(y-4)^2+(z-4)^2} =2· \sqrt{(x-6)^2+(y-3)^2+(z+1)^2}

(x+3)^2+(y-4)^2+(z-4)^2=4·[(x-6)^2+(y-3)^2+(z+1)^2]

x²+6x+9+y²-8y+16+z²-8z+16=4x²-48x+4y²-24y+4z²+8z+184

3x²+3y²+3z²-54x+16y+16z=-143

(x²-54x/3)+(y²+16y/3)+(z²+16z/3)=-143/3

(x²-54x/3+729/9)+(y²+16y/3+64/9)+(z²+16z/3+64/9)=-143/3+729/9+2·64/9

(x-27/3)²+(y+8/3)²+(z+8/3)²=428/9

We calculate a radius \sqrt{428/9} =6.89

Therefore, we conclude that the center of sphere at point

(27/3, -8/3, -8/3) with a radius 6.89.