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Why is 0≥1? (2 Viewers)

HeroicPandas

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Why is 0≥1?

I was working on a mathematical induction question and got stuck. I started to work backwards and ended up with this...
 

integral95

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Crap i don't remember how to do a formal proof
 

HeroicPandas

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Let predicate P(n) be ".."

Basis: For n=1, ...

Induction: suppose that k in positive integers
Suppose that P(k) is true

i.e. √1 + √2 + ... + √k ≥ 2/3 k√k

We want to deduce that P(k+1) is true

i.e. √1 + √2 + ... + √k + √(k+1) ≥ 2/3 (k+1)√(k+1)

We have

√1 + √2 + ... + √k + √(k+1)
≥ 2/3 k√k + √(k+1)
≥ 2/3 k√k + 2/3 √(k+1)



Discovery: our aim now is to prove that


Subtract both sides by 1 and combine square roots


Divide both sides by k and square both sides after


Multiply both sides by {k+1) as it is positive and then subtract both sides by k



OK that RED PART is a mistake, and the rest is wrong
 
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SpiralFlex

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Let predicate P(n) be ".."

Basis: For n=1, ...

Induction: suppose that k in positive integers
Suppose that P(k) is true

i.e. √1 + √2 + ... + √k ≥ 2/3 k√k

We want to deduce that P(k+1) is true

i.e. √1 + √2 + ... + √k + √(k+1) ≥ 2/3 (k+1)√(k+1)

We have

√1 + √2 + ... + √k + √(k+1)
≥ 2/3 k√k + √(k+1)



Our aim now is to prove that:

A few assumptions are circularity in the proof
 

SpiralFlex

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First of all after you say: "Our aim is to prove that", how did you go from that to the line below? Subtract 1 and say the square of the fraction is greater than the previous fraction?
 
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HeroicPandas

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First of all after you say: "Our aim is to prove that", how did you go from that to the line below? Subtract 1 and say the square of the fraction is greater than the previous fraction?

Counterexample when k = 1/3, the claim is false
Sorry, was a typo
 

SpiralFlex

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By your method if you fix up the error, it should factor out nicely.
 

SpiralFlex

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Does dividing both sides by k for this question mean that k=0........?



I have just edited my post
But you are assuming the truth of the inequality you are trying to prove. Let k = 1, is the inequality true?
 

SpiralFlex

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You should be good to go from here.













 
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