Question

Show whether √15 is rational or irrational.

Answer 1

√15 is an irrational number. You can show it by contradiction principle.
See your book. There would be an example showing √2 as irrational.you can do the same for √15.

Answer 2

√15 is irrational .because there is no root term for it.
for eg:√16= 4
4 is a rational number .