# Mathematical Proof

Watch this thread
Thread starter 5 months ago
#1
Is anyone able to help me prove the following is true? Where x & y are positive non-zero values

I tried writing a fraction with x+y on the top and proving that it's greater than 1, but to no success. Even tried rationalising the denominator but also no luck:

Thankyou
Last edited by beachpanda; 5 months ago
0
reply
5 months ago
#2
(Original post by beachpanda)
Is anyone able to help me prove the following is true? Where x & y are positive non-zero values

I tried writing a fraction with x+y on the top and proving that it's greater than 1, but to no success. Even tried rationalising the denominator but also no luck:

Thankyou
You might like to try looking for a counter-example.
1
reply
5 months ago
#3
(Original post by beachpanda)
Is anyone able to help me prove the following is true? Where x & y are positive non-zero values

I tried writing a fraction with x+y on the top and proving that it's greater than 1, but to no success. Even tried rationalising the denominator but also no luck:

Thankyou
if you let x and y both equal 1 see what happens
0
reply
Thread starter 5 months ago
#4
(Original post by the bear)
if you let x and y both equal 1 see what happens
I get 4<2 which isn't correct? But I've been told that x+y is greater than the other expression? (It formed part of a much longer question)

(Original post by ghostwalker)
You might like to try looking for a counter-example.
Do you know what sort of counter example? I could switch the inequality sign, or flip the fraction but I come into the same issues.
0
reply
5 months ago
#5
(Original post by beachpanda)
I get 4<2 which isn't correct? But I've been told that x+y is greater than the other expression? (It formed part of a much longer question)

Do you know what sort of counter example? I could switch the inequality sign, or flip the fraction but I come into the same issues.
the reason you cannot prove the statement is true is that it is false. unless there is some extra information about the value of x and y etc.
2
reply
5 months ago
#6
(Original post by beachpanda)
I get 4<2 which isn't correct? But I've been told that x+y is greater than the other expression? (It formed part of a much longer question)

Do you know what sort of counter example? I could switch the inequality sign, or flip the fraction but I come into the same issues.
Hopefully you've resolved this issue now.

As to a counter example, it's just a case of plugging some values in which make the assertion false, which is what you have done with the bear's suggestion. That's the counter-example disproving the assertion.
Last edited by ghostwalker; 5 months ago
0
reply
X

Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

### Poll

Join the discussion

#### Have you done work experience at school/college?

Yes (154)
41.85%
Not yet, but I will soon (68)
18.48%
No (146)
39.67%

View All
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.