## 1.1. Notation and Set Theory

### Examples 1.1.2(a):

If E = {

*x: x = 2n*for*n*N}, O = {*x : x = 2n - 1*for*n*N}, and I = {*x*R:*x*= -2}, then what, in your own words, do these sets represent ?^{2}- The set
**E**is the set of all even natural numbers. - The set
**O**is the set of all odd natural numbers. - The set
**I**consists of all real numbers whose square equals -2. Since there are no such real numbers, the set**I**is the empty set.