Question:
Write the following sets in roster from:
E = {x : x is a prime number, which is a divisor of 42}.
Solution:
Prime number = Those number which is divisible by 1 and the number itself.
Prime numbers are 2, 3, 5, 7, 11, 13, …
Divisor of 42 :
$42=1 \times 42$
$42=2 \times 21$
$42=3 \times 14$
$42=6 \times 7$
So, divisors of 42 are 1, 2, 3, 6, 7, 14, 21, 42
The elements which are prime and divisor of 42 are 2, 3, 7
So, E = {2, 3, 7}