Hint .
A plane goes trough a point and is parallel to two vectors what is the general equation?
The plane goes trough the point [2,3,1] and is parallel to the two vectors [1,2,3] and [2,3,-1].
The answer is 11x-7y+z-2=0
If I do the cross product of the two vectors I get the vector [-11,7,-1] which if multiplied by -1 corresponds to the answer but I dont thin that's the right way. :P