There is a very interesting proof technique called proof by contradiction. To do a proof by contradiction, we assume the opposite of what we want to prove and show that it leads to an impossible situation.
Mathematical proofs are one of the most b e a u t i f u l things that humanity has invented (or, as some will argue, discovered). A great proof convinces the reader of the validity of the claim and teaches her something fundamental about the nature of the problem domain.
There are a number of different proof strategies. This site focuses on just one.
There is a very interesting proof technique called proof by contradiction. To do a proof by contradiction, we assume the opposite of what we want to prove and show that it leads to an impossible situation.