Use resolution to show the hypotheses "Allen is a bad boy or Hillary is a good girl" and "Allen is a good boy or David is happy" imply the conclusion "Hillary is a good girl or David is happy."
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Let P = "Allen is a good boy"
Q = "Hillary is a good girl"
R = "David is happy"
Given:
~PVQ
PVR
Prove:
QVR
RVP
by Commutativity
~~RVP
by Double Negation
If ~R then P
by Material Implication
If P then Q
by Material Implication
If ~R then Q
by Hypothetical Syllogism
~~R V Q
by Material Implication
RVQ
by Double Negation
QVR
by Commutativity
Hence, it was proven. :D
Q = "Hillary is a good girl"
R = "David is happy"
Given:
~PVQ
PVR
Prove:
QVR
RVP
by Commutativity
~~RVP
by Double Negation
If ~R then P
by Material Implication
If P then Q
by Material Implication
If ~R then Q
by Hypothetical Syllogism
~~R V Q
by Material Implication
RVQ
by Double Negation
QVR
by Commutativity
Hence, it was proven. :D