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The equation of the plane is x-2y-2z=27. It can be written in the form enter image description here where d gives the distance of the origin from the plane, which I worked out to be 9 (can someone verify?). How do I work out the point which is the reflection of the origin? The answer is (6, -12, -12), but how do I get there?

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Hint-First find foot of orgin on that plane using equation of staright line passing through orgin and parelel to normal vecter.After that we have orgin and that point and knowing the relation of foot,point and reflection,you can find reflection

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Thank you, I've done that. I've got a second point P, with coordinates (-3,2,1), the reflection of that point in the plane is (5,-14, -15). Can you verify that for me? – Vladimir Nabokov Oct 27 '13 at 14:31
Yes.It is correct :-) – Half-Blood prince Oct 27 '13 at 16:53
Thank you so much!!! – Vladimir Nabokov Oct 27 '13 at 22:57

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