اذا كانت A equals open curly brackets 1 space comma space 2 space comma space 3 close curly brackets space space space comma space space B equals open curly brackets 2 space comma space 4 space comma space 5 close curly brackets فان A minus B equals
open curly brackets 1 space comma space 2 space comma space 3 close curly brackets space space
open curly brackets 2 space comma space 4 space comma space 5 close curly brackets
right to left empty set
open curly brackets space 1 space comma space 3 space close curly brackets