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Center and radius of a sphere

1. Homework Statement

The equation represents a sphere.

16x^2+16y^2+16z^2-96x+32y=5

Find its center, and radius



2. Homework Equations



3. The Attempt at a Solution
i found the center by completing the square:

16[(x^2-6x+9)+(y^2+2y+1)+(z^2)]=5+9+1
16[(x-3)^2 +(y+1)^2 +(z+0)^2]=15

the center is (3,-1,0)
i thought the radius would be (15^.5)/4 but that was incorrect if someone could please help me thank you
 

Answers and Replies

19
0
1. Homework Statement

16[(x^2-6x+9)+(y^2+2y+1)+(z^2)]=5+9+1
16[(x-3)^2 +(y+1)^2 +(z+0)^2]=15
You forgot to multiply the added 1 and 9 on the right side by 16. Either multiply everything out on the left side and see what needs to be added to equalize the right side or try going back and dividing everything by 16 before completing the square.
 
Last edited by a moderator:
ok i see what i did wrong. thank you very much
 

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