The Nx1 strategy tests N+1 points for each boundary inequality, N points on the boundary and 1 point off the boundary. The off point is chosen at or near the centroid of the on points. One must always be careful to choose the off point so that it is in a valid domain, i.e. one that leads to valid computations or to a specific error condition, otherwise the point may be
rejected for coincidental reasons, e.g. by an initial analysis that rejects all points not in a domain that leads to subsequent processing.
