平面解析几何对“求过二次曲线外的点所引曲线切线的方程”的问题，未给出一般的方法和公式。
The problem of attaining the tangent equation of a certain point on a quadratic curve is basically solved in plane analytical geometry.
二次曲线为非中心曲线的充要条件及方程表示形式。
The quadratic curve is the necessary and sufficient condition of the noncentral curve as well as the equation's representative form.
应用二次曲线束理论揭示解二元二次方程组的几何意义。
Apply the theory of pencil of conics to reveal the geometric significance of simultaneous equations of second degree with two unknows.
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