wills21
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Is anybody able to help me answer this, I'm completely stuck!
Thanks!
Prove by contradiction that there are no positive integers a and b, with a odd, such that

a + 2b = Root8ab .
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mqb2766
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(Original post by wills21)
Is anybody able to help me answer this, I'm completely stuck!
Thanks!
Prove by contradiction that there are no positive integers a and b, with a odd, such that

a + 2b = Root8ab .
Is that
sqrt(8ab)
or
sqrt(8)ab
Last edited by mqb2766; 1 year ago
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RDKGames
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(Original post by wills21)
Is anybody able to help me answer this, I'm completely stuck!
Thanks!
Prove by contradiction that there are no positive integers a and b, with a odd, such that

a + 2b = Root8ab .
Suppose there there is a pair of integers (a,b), with a odd, such that

a + 2b = \sqrt{8ab}

Then (a+2b)^2 = 8ab

Note that a+2b is (odd)+(even) hence it is (odd) and so the square (a+2b)^2 is odd ... but what's the problem ??
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wills21
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(Original post by mqb2766)
Is that
sqrt(8ab)
or
sqrt(8)ab
(8ab)
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wills21
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(Original post by RDKGames)
Suppose there there is a pair of integers (a,b), with a odd, such that

a + 2b = \sqrt{8ab}

Then (a+2b)^2 = 8ab

Note that a+2b is (odd)+(even) hence it is (odd) and so the square (a+2b)^2 is odd ... but what's the problem ??
that’s the question. simply “prove my contradiction” and it’s 4 marks (edexcel alevel maths)
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Interea
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(Original post by wills21)
that’s the question. simply “prove my contradiction” and it’s 4 marks (edexcel alevel maths)
Yes they've given you a big hint, they're asking you what the problem is (i.e. can you spot the contradiction now?)
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Ryan0887
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Ahh just spotted it
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llleahll
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(Original post by wills21)
Is anybody able to help me answer this, I'm completely stuck!
Thanks!
Prove by contradiction that there are no positive integers a and b, with a odd, such that

a + 2b = Root8ab .
where can i find this question paper? thanks
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llleahll
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(Original post by llleahll)
where can i find this question paper? thanks
is it aqa or edexcel?
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dnejfn
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anyone know what paper this question is from?
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Tere_108
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I think it is the Edexcel 2020 mock paper set 2 but only teachers can access it.
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Hasan167
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any answer to this?
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davros
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(Original post by Hasan167)
any answer to this?
Do you mean the original question? That was answered a year ago in post #3
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Aspiring97
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Bb
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JESSEMFUNDA
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Look at all the people here trying to cheat, loooooollllll
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olliebrown6
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(Original post by RDKGames)
Suppose there there is a pair of integers (a,b), with a odd, such that

a + 2b = \sqrt{8ab}

Then (a+2b)^2 = 8ab

Note that a+2b is (odd)+(even) hence it is (odd) and so the square (a+2b)^2 is odd ... but what's the problem ??
But the question doesn’t clarify whether b is odd or even, and if b is also odd then surely the equation can work?
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mqb2766
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(Original post by olliebrown6)
But the question doesn’t clarify whether b is odd or even, and if b is also odd then surely the equation can work?
Trying out a few numbers may be useful?
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charliebrett14
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(Original post by olliebrown6)
But the question doesn’t clarify whether b is odd or even, and if b is also odd then surely the equation can work?
Yes but it doesnt matter what b is, as it is 2b it is a multiple of 2 and a multiple of two always even e.g if b is 3 2b is 6 which is even etc
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Runningman99
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(Original post by wills21)
Is anybody able to help me answer this, I'm completely stuck!
Thanks!
Prove by contradiction that there are no positive integers a and b, with a odd, such that

a + 2b = Root8ab .
By any chance do you remember what question paper this is from
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Runningman99
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(Original post by wills21)
that’s the question. simply “prove my contradiction” and it’s 4 marks (edexcel alevel maths)
Do you know the specific paper??
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