1. Two marks example problems I

Let $X = \{1$, $2$, $3$, $4\}$ and $Y = \{2$, $4$, $6$, $8$, $10\}$ and $\mathbb{R} = \{(1, 2)$, $(2, 4)$, $(3, 6)$, $(4, 8)\}$. Show that $\mathbb{R}$ is a function and find its domain, co-domain, and range?

 

$\mathbb{R}$ is a functionnot a function.

 

Domain $=$ $\left\{i,i,i,i\right\}$

 

Co-domain $=$ $\left\{i,i,i,i,i\right\}$

 

Range $=$ $\left\{i,i,i,i\right\}$