Co :60=2².3.5

72=2³.3²

»UCLN(60,72)=2².3=12

»UC (60,72)=U(12)={1,2,3,4,6,12}.

b)B={x€N/x:12,x:15,x:18 va 0<x<300}

Vi:x:12,x:15,x:18

»x€BC(12,15,18)

Co: 12=2².3

15=5.3

18=3².2

»BCNN(12,15,18)=2².3².5=180»BC(12,15,18)=B(180)={0,180,360,...}

Vi: 0<x<300»x=180

»B={180}

Cau 2:

Co: 12=2².3

28=2².7

BCNN(12,28)=2².3.7=84

BC(12,28)=B(84)={ 0,84,168,252,336,.....}

Phan b cau tu lam nhe .co j thac mac thi nhan tin cho mk

a, 72 = 2³.3²;    24 = 2³.3 

ƯCLN(72; 24) = 2³.3 = 24

ƯC(72; 24) = { 1; 2; 3; 4; 6; 8; 12; 24}

b, 30; 60; 20

 30 = 2.3.5;                 60 = 2².3.5;                 20 = 2.5

 ƯCLN(30; 60; 20) = 2.5 = 10

ƯC(30; 60; 20) = { 1; 2; 5; 10}

Bài 1: 

a: UCLN(12;52)=4

UC(12;52)={1;2;4}

giúp mik với nha

khó thế

a , Ta có :
a = 15 = 3.5
b  = 25 = 5²
c = 30 = 2 . 3 . 5
UCLN(a ,b,c ) = 5 
Ưc (a , b ,c )=Ư(5) = 1;5
b, Ta có 
a = 15 = 3.5
b  = 25 = 5²
c = 30 = 2 . 3 . 5
BCNN = 3 . 2. 5² = 150 
BC (a,b,c) = B( 150) = 150 , 300 , 450 ,...
Chúc bạn học tốt !
 

a. 15 = 3 . 5

25 = 5²

30 = 2 . 3 . 5

=> ƯCLN (15, 25, 30) = 5

=> ƯC (15, 25, 30) = ƯC (5) = {1; 5}

b) 15 = 3 . 5

25 = 5²

30 = 2 . 3 . 5

BCNN (15, 25, 30) = 2 . 3 . 5² = 2 . 3 . 25 = 150

BC (15, 25, 30) = BC (150) = {0; 150; 300; ...}

Ta co : BCNN(a;b). UCLN)a;b)=a.b=12.336=4032

Vi UCLN(a;b)=12

Dat a 12x: b=12.y voi UCLN(x;y)=1 ma a.b =4032 hay 12x.12y =4032

144.(x.y)=4032 

Suy ra :x.y=28

Cap so nguyen to cung nhau co tich bang la : (28;1) va (7;4)

khi : x=28;y=1 thi a=336 va b=12

khi x=7 ; y=4 thi a=84 va b=48

**** nhe

a=48 b=84 

a=24 b=168