If A 1 2 3 4 and B 4 5 6 7 what is A B?

The expression ( A B ) typically denotes the concatenation of the two sets A and B. Therefore, if ( A = {1, 2, 3, 4} ) and ( B = {4, 5, 6, 7} ), then ( A B ) would represent the combined set of elements from both A and B, which is ( {1, 2, 3, 4, 5, 6, 7} ).