Write the negation of each of the following. Only students eat pizza. There exists something, which is not a student, that eats pizza. Every student eats pizza. There exists a student which does not eat pizza.
Some students eat only pizza.
No student only eats pizza. Decide whether each of the following wffs is valid or invalid. Justify your answer. The above statement is a simple case of double negation. The hypothesis is then true, but not the conclusion.