Question

If A = {positive integers} and B = {…,−4, −3, −2, −1} what is A ∩ B?

{ }

{…, −3, −2, −1, 1, 2, 3, …}

{1, 2, 3, 4, …}

{…−3, −2, −1}

Answer 1

A ∩ B contains all the elements that are both in A AND B. Since there is no positive integer in B the two sets are said to be disjoint and A ∩ B contains nothing. So you can write A ∩ B = {}