过A做AK⊥BC
AD²=AK²+DK²
AB²=AK²+BK²
AD²-AB²
=AK²+DK²-AK²-BK²
=DK²--BK²
=(DK+BK)(DK-BK)
==(DK+CK)(DK-BK)
=CD×BD
(2)同样的做法
AB²-AD²=AK²+BK²-AK²-DK ²
=BK²-DK²
=(BK+DK)(BK-DK)
=(CK+DK)(BD
=(CD×BD
过A做AK⊥BC
AD²=AK²+DK²
AB²=AK²+BK²
AD²-AB²
=AK²+DK²-AK²-BK²
=DK²--BK²
=(DK+BK)(DK-BK)
==(DK+CK)(DK-BK)
=CD×BD
(2)同样的做法
AB²-AD²=AK²+BK²-AK²-DK ²
=BK²-DK²
=(BK+DK)(BK-DK)
=(CK+DK)(BD
=(CD×BD