Use method of direct proof to prove the statement
65757
Prove that $n! + k$ is a composite number
148790
Basic question about proofs with the goal $\exists x P(x)$
98537
What is wrong with the proof?
48368
Prove using Natural Deduction in predicate logic $(\forall x\ P(x))\to Q ⊢ \exists x (P(x)\to Q)$
155897
Proof by induction - is this correct?
88188
Explain proof by contradiction.
31091
Prove that there exist a branch
121720
Given ∃x.¬p(x), use the Fitch System to prove ¬∀x.p(x).
104492
Why is complete strong induction a valid proof method and not need to explicitly proof the base cases?
101899
Proof By Induction of a Sum
6113
Proof of Strong principle of Induction (T. Tao Analysis I)
23869
Prove the implication "if $ac>bc$ and $c>0$, then $a>b$" using the contrapositive
104124
Prove or disprove: $A-(B-C) = (A-B)-C$
16384
Proving a result in a given field
147375
Prove :(P → Q) ∨ (Q → P) using natural deduction
51877
Why is this 'Proof' by induction not valid?
9282
Prove using natural deduction $((P \land Q) \rightarrow R) \vdash (P \rightarrow R) \lor (Q\rightarrow R)$