Prove if true and find a counterexample if false (disproofs/algebraic proofs)
139841
Proving $A\setminus(B\setminus C)$ is not equal to $(A\setminus B)\setminus C$
112539
Can I disprove a claim using the contrapositive?
126633
Is a contradiction enough to prove a set equality to $\varnothing$?
151356
Need Hints Prove "$((\neg \alpha \to \alpha) \to \alpha) $" Using Axiom 1,2,3 and MP and deduction theorem
106305
Prove/disprove: if $\det(A+X) = \det(B + X)$ for all $X$, then $A=B$
157625
How to prove conditional in Coq?
3663
Finding counterexamples in elementary set theory.
125754
Proving or disproving a statement about continuity and limits
10598
Contrapositive Fitch Proof
52322
Implication in mathematics - How can A imply B when A is False?
49453
Why do I have to solve for $x$ in this proof, if I choose not to find a counterexample?
119888
Is it possible to convert $\forall$ quantifiers to $\exists$ quantifiers without negation?
65895
Irrationality proofs not by contradiction
141496
Could someone make the proof into a hinted exercise?
113344
How do we prove that something is unprovable?
140194
Using natural deduction to prove that $p \implies q \vdash \lnot p \lor q$
120517
Is it possible to prove that a particular statement cannot be disproved without creating a contradiction?