If $p$ is a prime number and $p$ divides $a^2$, then which conclusion must be true?
- $p$ divides $a$
- $a$ must be prime
- $a$ must equal $p$
- $p$ divides only even numbers
Show answer and solution
Correct answer: A. $p$ divides $a$
This is a standard theorem based on prime factorisation: if a prime divides $a^2$
then that prime must already occur in the factorisation of $a$.
**Hence $p$ divides $a$.**