see example 1 here
no you don't ...it can't be doneI know how to work out with the two pionts but not three
and if you could, why didn't you just ignore the third point and do it?
A plane can be defined as:
where is a point on the plane and is the normal vector.
Let points A, B, C be (1,2,7), (2,3,4) and (-1,2,1) respectively.
Notice that the plane contains vectors and and their cross product will give the normal vector perpendicular to it.
So find to get (a,b,c) and use one of A, B, or C for your .
Now, again, plug it all into: