A = {1, 2, 3, 5} and B = {4, 6, 9}.
Question:

$A=\{1,2,3,5\}$ and $B=\{4,6,9\}$. Define a relation $R$ from $A$ to $B$ by $R=\{(x, y)$ : the difference between $x$ and $y$ is odd; $x \in A, y \in B\}$. Write $R$ in roster form.

Solution:

$A=\{1,2,3,5\}$ and $B=\{4,6,9\}$

$\mathrm{R}=\{(x, y):$ the difference between $x$ and $y$ is odd; $x \in \mathrm{A}, y \in \mathrm{B}\}$

$\therefore R=\{(1,4),(1,6),(2,9),(3,4),(3,6),(5,4),(5,6)\}$