You are Here: Home >< Maths

# Proof by contradiction appropriate? watch

1. I had an exam question that went like:
"Prove that, for all real numbers:

x^2 + 2Px + q^2 - p^2 = 0

Other people who did the exam used the discriminant but I used proof by contradiction. Is this appropriate?

i.e.

Assume it is wrong and then find a counterexample instead.
2. (Original post by Seppuku)
I had an exam question that went like:
"Prove that, for all real numbers:

x^2 + 2Px + q^2 - p^2 = 0

Other people who did the exam used the discriminant but I used proof by contradiction. Is this appropriate?

i.e.

Assume it is wrong and then find a counterexample instead.
""Prove that, for all real numbers: x^2 + 2Px + q^2 - p^2 = 0" doesn't make any sense. Since you mentioned the discriminant, presumably the question mentioned something about the number of roots. Please post the complete question so that I can help you further.
3. (Original post by Seppuku)
I had an exam question that went like:
"Prove that, for all real numbers:

x^2 + 2Px + q^2 - p^2 = 0

Other people who did the exam used the discriminant but I used proof by contradiction. Is this appropriate?

i.e.

Assume it is wrong and then find a counterexample instead.
]

Proof by contradiction isn't really about finding a counterexample, but more generally a contradiction of any kind.

### Related university courses

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: May 26, 2018
The home of Results and Clearing

### 2,934

people online now

### 1,567,000

students helped last year
Today on TSR

### University open days

1. Sheffield Hallam University
Tue, 21 Aug '18
2. Bournemouth University
Wed, 22 Aug '18
3. University of Buckingham
Thu, 23 Aug '18
Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams