negative semi-definite quadratic form

The conditions of equivalence of negative definite quadratic form and negative semidefinitequadratic form are given according to their definitions and some properties of negative definitematrices are given too in the paper.

本文根据负定二次型与半负定二次型的定义给出了它们的若干等价条件,并讨论了负定矩阵的若干性

The conditions of positive semidefinite quadratic form are given according to its definition,and some properties of postive semidefinite matrix are given according to its definition in the paper.

从半正定二次型的定义出发 ,推导出与其定义等价的几个条件 ;并且根据半正定矩阵的定义 ,推导出半正定矩阵的若干性