vertex of a quadric

例句：

1. 1.The quadric equation is a form of polynomial equation.
   四元方程是一种多项式方程的形式。
2. 2. The quadric surface is a type of surface with four corners.
   四棱面是一种具有四个角的表面类型。
3. 3.The quadric function is a mathematical function that describes the shape of a quadric surface.
   四棱函数是一种描述四棱面形状的数学函数。