¦^ÅU¤@¤U ¤¤ªº Euclid's Algorithm ¥i¥H»¡¬O¥ô¨ú a, b , ¨ä¤¤ b 0, «h¦s¦b h, r , ¨ä¤¤ r ²Å¦X r = 0 ©Î r < b ¨Ï±o a = b . h + r. ¦Ó¦b F[x] ¤¤ªº Euclid's Algorithm ¬O»¡¥ô¨ú f (x), g(x) F[x] ¨ä¤¤ g(x) 0, «h¦s¦b h(x), r(x) F[x], ¨ä¤¤ r(x) ²Å¦X r(x) = 0 ©Î deg(r(x)) < deg(g(x)) ¨Ï±o f (x) = g(x) . h(x) + r(x). ³o¸Ì«nªº¬O¦b ¤¤¦³¤@Óµ´¹ïȨç¼Æ±N ¤¤ªº«D 0 ¤¸¯À°e¨ì«Dtªº¾ã¼Æ, ¦Ó¦b F[x] ¤¤¦³¤@Ó degree ¨ç¼Æ±N F[x] ¤¤ªº«D 0 ¤¸¯À°e¨ì«Dtªº¾ã¼Æ. §ÚÌ´N¬OnÂ^¨ú³o¼Ëªº¨ç¼Æªº¯S©Ê.
°£¤F ©M F[x] ¥ ÁÙ¦³³hªº Euclidean domain. ¨Ò¦p [i] = {a + bi | a, b } ³o¤@Ó integral domain §Q¥Î (a + bi) = a2 + b2 ³oÓ¨ç¼Æ´N¥i±o [i] ¬O¤@Ó Euclidean domain (¦b¦¹§Ú̲¤¥hÃÒ©ú, Y¦³¿³½ìªº¦P¾Ç¥i¨ìºô¯¸ http://math.ntnu.edu.tw/li/note ¤U¸üÁ¿¸q ``Factorization of Commutative Rings'' ¦³¸Ô²ÓÃÒ©ú).
¤@¯ë¦Ó¨¥nÅçÃÒ¤@Ó integral domain ¬O§_¬°¤@Ó Euclidean domain ¬O«Ü§xÃøªº. ¦b¦¹§Ų́䣰Q½×³oÃþªº°ÝÃD. §Ú̶ȦC¥X Euclidean domain ªº«n©Ê½è. ¦^ÅU§ÚÌ´¿§Q¥Î Euclid's Algorithm ÃÒ¥X¦b ©M F[x] ¤¤©Ò¦³ªº ideal ³£¬O principle ideal. ³o¤@®MÃÒ©ú¥i¥H§¹§¹¾ã¾ã·h¨ì Euclidean domain ¤W.
¥Ñ©ó d I, ¦ÛµM±o d I. ¥t¥ ¹ï¥ô·N a I, ¥Ñ Euclidean domain ªº°²³]ª¾¦s¦b h, r R º¡¨¬ a = d . h + r ¥B r = 0 ©Î (r) < (d ). ¦pªG r 0, ¥Ñ r = a - d . h ¥B a, d I ¥iª¾ r I. ¤]´N¬O»¡ r I {0} ¥B (r) < (d ). ³o©M (d ) ¬O T ¤¤³Ì¤pªº°²³]¬Û¥Ù¬Þ, ¬Gª¾ r = 0. ´«¨¥¤§ a = d . h, §Y a d. ¬G±oÃÒ I d.
¥Ñ©ó¤@Ó integral domain ªº ideal ³£¬O principle ideal ³o¼Ëªº ring «D±`¯S§O, §Ṳ́]µ¹¥¦¤@Ó¯S§Oªº¦WºÙ.
Theorem 8.2.2 §i¶D§Ṳ́@Ó Euclidean domain ¤@©w¬O¤@Ó principle ideal domain. nª`·N, £¸Ó principle ideal domain ¥¼¥²·|¬O¤@Ó Euclidean domain. ¦³¿³½ìªº¦P¾Ç¥i¥H°Ñ¦Ò§ÚªºÁ¿¸q ``Factorization of Commutative Rings'' ¨ä¤¤¦³µ¹¤@Ó principle ideal domain ¦ý¤£¬O Euclidean domain ªº¨Ò¤l.