The answers to exercises marked [BB] can be found in the Back of the Book.List five elemen...

The answers to exercises marked [BB] can be found in the Back of the Book.

List five elements in each of the following sets:

(a) [BB1 {a + bi | a, b ∈ Z, i2 = −1}

(b)

(c)

(d) {n ∈ N | n2 + n is a multiple of 3}