Question:
Write the relation $\mathrm{R}=\left\{\left(x, x^{3}\right): x\right.$ is a prime number less than 10$\}$ in roster form.
Solution:
$\mathrm{R}=\left\{\left(x, x^{3}\right): x\right.$ is a prime number less than 10$\}$
The prime numbers less than 10 are $2,3,5$, and 7 .
$\therefore R=\{(2,8),(3,27),(5,125),(7,343)\}$