容易证明:同一条直线上顺次是A、B、C、D的四点构成线段|AB|=|CD|的充要条件是线段AD与BC的中点重合。在解证有关直线与二次曲线和交所得的线段相等的问题时,合理使用上述关系式,可避开求交点坐标,计算距离等繁杂的运算,使问题转 It is easy to prove that the four-point line segment |AB|=|CD| in the order of A, B, C, and D on the same line is a necessary and sufficient condition that coincides with the midpoints of line segments AD and BC. When solving the problem that the straight line is equal to the quadratic curve and the resulting line segment, the rational use of the above relational expression can avoid the complicated operations such as finding the coordinates of the intersection point, calculating the distance, etc.