Question

如图，A、B、C、D是直线L上顺次的四点，且AC=5，BD=4,求线段AB-CD的值

图
——a————b—c———d——L
要完整的
因为 所以的形式
∵
∴

Answer 1

∵ AB=AC-BC, CD=BD-BC
∴AB-CD=AC-BC-BD+BC
=AC-BD
=5-4
=1

Answer 2

设bc = x,有ab = ac - bc = 5 - x,cd = bd - bc = 4 - x,

ab - cd = (5 - x) - (4 - x) = 1或∵ AB=AC-BC, CD=BD-BC
∴AB-CD=AC-BC-BD+BC
=AC-BD
=5-4
=1

Answer 3

∵AB-CD=(AB+BC)-(CD+BC)
=AC-BD
∴AB-CD=1

Answer 4

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