Explicație pas cu pas:
a)N; N={0,1,2,3,4.....}
b)N*={1,2,3,4,....}
a)mai mare ca zero
b)Z={...-3, -2, -1, 0, 1, 2,3....}
c)Z/{0}=Z*
d)Z*_={...-3,-2,-1}
e)Z*+={1,2,3,4,5....}