Question

Write the following sets in the roaster form.
A = {x | x is a positive integer less than 10 and 2^x – 1 is an odd number}

Answer 1

2^x – 1 is always an odd number for all positive integral values of x.

In particular, 2^x – 1 is an odd number for x = 1, 2, ..., 9.

Thus, A = {1, 2, 3, 4, 5, 6, 7, 8, 9}.