a)D30={1,2,3,5,6,10,15,30}
D18={1,2,3,6,9,18}
D30-D18={1,2,3,5,6,10,15,30} - {1,2,3,6,9,18}={5,10,15,30<
b)D40 n D60
D40={1,2,4,5,8,10,15,20,40}
D60={1,2,3,4,5,6,10,15,20,30,60}
D40 n D60={1,2,4,5,8,10,15,20,40} n {1,2,3,4,5,6,10,15,20,30,60}={1,2,4,5,10,15,20}
Nota:
n=reunit
Sper ca ti.am fost de ajutor !