巧求锥面方程

A Knack for Getting an Taper Faced Equation

已知锥面的顶点及准线求锥面方程,将准线变形为含有(x-a),(y-b),(z-c)因子的方程,设法配成齐次方程后加以整理得到锥面方程.

To make out a Taper Faced Equation（TFE） while known the vertex and directrix of the taper, by transforming the directrix equation to another form in which has such factors as （x-a）, （y-b）, （z-c）, we try to get an equal power equation, then rectify it to be the TFE.