... vµ 72; a) 40 = 23 .5 ; 60 = 22 .3.5 c) 13 vµ 20 ; BCNN(40 ,60 ) = 23 .3.5= 120 d) 28 , 29 vµ 35 b) 36 = 22 . 32 ; 60 = 22 .3.5 ; 72 = 23 . 32 BCNN( 36, 60, 72) = 23 . 32. 5 = 360 c) 13 vµ 20 lµ hai sè nguyªn ... cïng nªn: ¦CLN (28 ,29 ,35) = Bµi 9: a) 90 = 2. 32. 5 ; 1 26 = 2. 32. 7 ¦CLN(90,1 26 ) = 2. 32 = 18 ¦C(90,1 26 ) = {1; 2; 3; 6; 9; 18} b) 108 = 22 .33 ; 180 = 22 . 32. 5 ¦CLN(108,180) = 22 . 32 = 36 ¦C(108,180) ... 60 = 22 .3.5 ¦CLN(40 ,60 ) = 22 .5 = 20 b) 36 = 22 . 32 ; 60 = 22 .3.5 ; 72 = 23 . 32 ¦CLN( 36, 60, 72) = 22 .3 = 12 c) 13 vµ 20 lµ hai sè nguyªn tè cïng nªn: ¦CLN(13 ,20 ) = d) 28 ,29 vµ 35 lµ ba sè nguyªn...