HW #2

pg. 27 (1)(h),
pg. 41 (1)(f),
Also prove the following sequents are valid:
(PV(Q&R)) |- ((PVQ)&(PVR))
(P&Q) |- ~(P->~Q)
Extra Credit (Hard!):
Prove that PVQ,~P |- Q is valid without copying the proof
from Lemmon.