Finding the Closest Point on a Plane to a Given Point

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Homework Statement


Find the point on the plane x-y+z=4 closest to the point (1,2,3).

d=\frac{2}{\sqrt{3}}

Homework Equations



Hmm...

The Attempt at a Solution



As you can see, I've already solved for the shortest distance. But, knowing the plane I'm on and the distance, how do I find the point that lies on that plane, at that distance from (1,2,3)? Help...
 
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Embed the point into a plane with the same normal vector as the given plane.

The shortest distance from the origin to any plane ax +by +cz = d is
\frac{|\mathbf{n}|}{d} where \mathbf{n} is the normal vector to the plane.

Do this for both the given plane and your new plane from and calculate the difference.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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