Liste des Groupes | Revenir à ol advocacy |
A is all prime numbers <= 100The second and fourth cases should both be false, not true.
B is all odd numbers <= 100
We have 4 possibilities:
A => B: true
A number is prime implies it is odd. Another, more proper,
way to state this is that if a number is in set A (prime)
then it is also in set B.
~A => B: true
If a number is not prime then it is odd. The set of ~A
includes all the even numbers as well as all the odd numbers
in B. This statement actually says that a number being not
prime as well as odd is a possibility because ~A includes B.
A => ~B: false
Obviously, if a number is prime it cannot be not odd, that is,
if a number is in set A (prime) it cannot be in set ~B (even
numbers).
~A => ~B: true
Again, if a number is not in set A, the evens and all non-prime
odds, then it may be also not in set B, the non-prime odds.
Les messages affichés proviennent d'usenet.