Question

Let S = {2,4,6} and T = {1,3,5}. Use the set-roster notation to write each of the following sets, and indicate the number of elements that are in each set?

a. S X T

b. T X S

c. S X S

d. T X T

The problem is I don’t know what’s flying here, there are no examples in the book that can help.

Answer 1

I am fairly confident that S X T is supposed to be interpreted as S × T, the Cartesian product of S and T. This is the set of all pairs whose first element comes from S and whose second element comes from T. Given that S = {2, 4, 6} and T = {1, 3, 5}, this would be the set

{ (2, 1), (2, 3), (2, 5), (4, 1), (4, 3), (4, 5), (6, 1), (6, 3), (6, 5) }

Using this as a starting point, you should be able to answer parts (b) through (d). The term “set-roster notation” refers to the notation of just listing off all the elements one at a time, as I’ve done above.

Hope this helps!