56=2³.7​​​

a. 140=2².5.7

thừa số nguyên tố chung là 2;7

ƯCLN [56;140]=2².7=28

b. 24=2³.3

84=2².3.7

180=2².3².5

thua so nguyen to chung la 2;3

UCLN[24;84;180]=2^2.3=12

c. 60 la Ư[180] nên ƯCLN[60;180]=60

d. 19 la so nguyen to nen UCLN[15;19] = 1

chuc ban hoc gioi