If (n^2-4n) is odd, where n i positive integer, then n is odd. By contradiction

Question

I need help getting started

Answer 1

When you are asked to prove by contradiction you should follow the following flow:

1. Assume the opposite of what you are trying to prove
2. Make logical inferences using the assumption from step 1
3. You will eventually find a contradiction (aka "prove" something that you know is not true) this, therefore, means that your original assumption was incorrect.

For your problem try something like this:

1. Assume n is even (the opposite of what you are trying to prove)
2. Make logical inferences using the assumption from step 1
3. You will eventually find a contradiction (hint: think about (n^2-4n)). This proves that your assumption was false and n in fact is odd