Difference between domain and co-domain in sets? Let's say I have a subset of the Cartesian plane, for example:
$\{(x, y) \in R \times R: 2x+3 > 5\}$.
If I am asked to find the co-domain of the following set, how would I do so? I know how to find the domain, which is done by finding all possible $(x,y)$ ordered pairs and then placing all the $x$ values in a set. But how is this different from the co-domain?
Thank you very much!

Normally, domain and co-domain are defined on functions, but we'll use your textbook's definition for domain and co-domain on relations.
In your relation, note that your set describes only the $x$-values, $2x+3>5$, i.e. $x>1$. So the $x$-values that satisfy this condition is your domain, as defined in your textbook. However, since there is no condition on your $y$-values, all of $\mathbb{R}$ is your co-domain.
