i need help with this quick pls , please solve 5a

Answer:
Step-by-step explanation:
If you use de morgan's laws to write out [tex]-(PvQ)[/tex], it returns -P ^ -Q
And if ^ means 'and', it is showing that (P and Q) and (-P and -Q) which isn't possible since there can't be something that is both true and false. Therefore, it is a contradiction since something can not be true a nd false at the same time.