Hello, I get confused while solving the examples which have Existetial and universal specification/generalization.
Can anyone help me to solve my doubts,
1)When to assume variable as fixed?
e.g.1) Q(x,y,z) is "x+y = z" for real numbers. which is true?
s1 : $\forall x\forall y\exists z$ Q(x,y,z)
s2: $\exists z\forall x\forall y$ Q(x,y,z)
In above example where who should consider 'z' as fixed. What is th rule?
e.g 2) $\forall x$ {P(x) $\vee$ Q(x)}
$\exists x$ (negation (P(x))
$\forall x$ {negation (Q(x)) V R(x)}
$\forall x$ {S(x) -> negation(R(x))}
what should be the answer $\exists x $ negation(S(x)) or $\forall x$ negation(S(x))?
