Math Is Fun Forum

PatternMan

Member

Registered: 2014-03-08

Posts: 199

Can anyone prove this = or non equal?

n
------
x - y   

= or not = 

n+y
------
   x

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"School conditions you to reject your own judgement and experiences. The facts are in the textbook. Memorize and follow the rules. What they don't tell you is the people that discovered the facts and wrote the textbooks are people like you and me."

ShivamS

Member

Registered: 2011-02-07

Posts: 3,648

Re: Can anyone prove this = or non equal?

By ----- do you mean divide?

Bob

Administrator

Registered: 2010-06-20

Posts: 10,637

Re: Can anyone prove this = or non equal?

hi

You only need one counter example to prove it is false.  Try choosing some numbers for n, x and y.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

ShivamS

Member

Registered: 2011-02-07

Posts: 3,648

Re: Can anyone prove this = or non equal?

If you do, it's false. Counterexample: n, x is 2, y is 1
2/(2-1) doesn't equal (2+1)/2

PatternMan

Member

Registered: 2014-03-08

Posts: 199

Re: Can anyone prove this = or non equal?

If you do, it's false. Counterexample: n, x is 2, y is 1
2/(2-1) doesn't equal (2+1)/2

This is proof by what? So you only need one instance of a counterexample to prove it's false but you need to use variables to prove something is true. Well I found I found some numbers that made it true and I was going to use it to solve a problem but realized that it might not be true for all numbers and turns out it isn't.

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"School conditions you to reject your own judgement and experiences. The facts are in the textbook. Memorize and follow the rules. What they don't tell you is the people that discovered the facts and wrote the textbooks are people like you and me."

ShivamS

Member

Registered: 2011-02-07

Posts: 3,648

Re: Can anyone prove this = or non equal?

To prove it false, you need only one counterexample. To prove it true, there are several methods like contradiction, induction. A great book on proofs is How to Prove It: A Structured Approach by Daniel J. Velleman.