mat quan he thu to.
Vi dy. 1) Quan he E trong tap hop cac s6 to nhieh N la mat quan he thu to. mat quan he thu to.
2) Quan he chia het trong N : ngded ta Id hieu al b va dee "a chia het b".
3) Quan he bao ham C gifta cac be phan eta met tap hop X Trong vi du 1), vol a va b try y to luon cd a g.. 6 Ileac a. NgUdi ta gel met quan he that to nhu thy la town phan.
Trong vi du 2) khong plied ta hien luen cd al b hoac It( a ved a,
b thy y, clang Ilan vai a = 2 VA. b = 3. Dieu dd cling thy ra vat vi du 3). Ngudi ta ban I vat C la tinting quan he thd to
60 ph4n.
Neu S la mot quan he thd tut trong X, thi rived ta thudng Id hieu S bang g.. (bat chub° ki hieu quan he thil to thong tinging eta s6 nguyen hay s6 flute) va doe a g b la "a be hon
b". Ngubi ta coi b .?•.- a la clang nghia vet a g 6 va doe la "6
Ion hem a". Ngdoi ta con viet a < b (hay b S a) quan he
va. a # 6" va doe la "a thtte su be ban b" hay "6 thAlc ski lon hon a".
Dinh nghia 7. Gia. su X lit met tap hop sap thd W. Met phgn tit a e X gei lit phdn to t6i ties (phan to t61 dal) eta X
neu quan hex # a Ix a) kat) theo x = a.
Vi d,. 1) Trong tap hop cat se to nhien thve stt len lam I, sap that to theo quan he I (quan ha chia het), the Olin tit tOi tigu la the s` nguyen
2) Trong tap hop cat he theta doe lap tuyen tinh eta khong gian vecto IV sap tint W theo quan he bao ham C, cac ha \recto gem rt \recto la t61
3) Tap hop cac se thuc, ved quan he that to thong thudng, khong cd plign to t6i dai cling khong cd phan to tei tidu.
Dinh nghia S. Girl sit X la met tap hop sap that tu. Mot phgn tit a E X get la phlin tti be nit& titan to lan nhgt) coo.
X nen, vet mot x E X, to cd a E x( x g a).
Neu met tap hop X sap thd to cd met phtin tit be nhat a thi a la phtin to be nhgt duy nhgt. That thy gib sit 5 6 la phtin to be nhgt, ta suy ra a < b va 6 # a, We la a = 6.
Cling nhan get nhu thy del veil phan ta len nhgt.
Vi dzt.• 1) Tap hop the s6 to nhien sap thit tp theo quan he eq phtin tit be nhgt IA 1 va OHM to Ion nhat IA 0. Neu sap