The first step of an indirect proof is to assume the opposite, or negation, of the given statement.
Assume temporarily that n is divisible by 2.
Practice makes perfect
The first step of an indirect proof is to assume the opposite, or negation, of the given statement. Let's think about the second part of the given statement.
nis not divisible by 2.
To write a negation of this statement, we need to consider how to say its opposite. Since we already have not within the sentence, we can negate the sentence by removing it.
Negation: & n is divisible by2.
Since the first step is to temporarily assume the opposite, we should include this fact in our sentence.
First step:
Assume temporarily that n is divisible by2.
