intervalale inchise [,inseamna ca se ia si valoarea de capat
la intervalele deschise ( ,nu se ia valoarea de capat
reuniune U inseamna toate valorile
intersectie ca la intersectia a doua strazi doar valorile comune
[-4,10)={-4,-3,-2,-1,0,1,2,3,4,5,6,7,8,9}=A
[0,15)={0,1,2,3,4,5,6,7,8,9,10,11,12,13,14}=B
AUB={-4,-3,............................14} de la -4 la 14
A∧B(este un u intors)={0,1,2,3,4,5,6,7,8,9}
