We give a sufficient and necessary condition for negative correlations.

我们得到判定概率测度是负相关的一个充分必要条件.

We propose a sufficient and necessary condition of the paradox production.

提出产生悖论的一个充要条件；

Meanwhile, the sufficient and necessary condition for the orientation of an arbitrary simple polygon is given.

同时, 给出了任意简单多边形走向的充要条件.

In this paper, we give sufficient and necessary condition and some sufficient conditions of oscillate for neutral differential equations with piecewise constant argument.

研究了一类具有分段常数变元的中立型微分方程组的振动性，并给出了所有解振动的充分必要条件和若干充分条件。

A sufficient and necessary condition for the existence of solution of is determined, followed by the representation of the general solution.

并给出了其有解的充要条件和通解的表达式。

The problem of knots removal for B-spline curves is investigated in this paper. The sufficient and necessary condition for removing knots of B-spline curves exactly is simplified.

研究了B样条曲线节点的消去问题，简化了B样条曲线内部节点精确消去的充要条件。