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(φ)^√2 and (√2)^φ (Posted on 2024-05-31) Difficulty: 3 of 5
Without direct evaluation, determine which of these following expressions is larger:

(φ)√2 and (√2)φ

No Solution Yet Submitted by K Sengupta    
Rating: 3.0000 (1 votes)

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Possible Solution Comment 1 of 1
Assume it is known that 1<√2<φ<2, but not their exact values.

Call the expressions:
(φ)^√2  (I) 
(√2)^φ  (II)   

Multiply I and II  by (√2) and square:

((√2)*((φ)^√2))^2 =  2φ^(2√2)   
((√2)*((√2)^φ))^2  = 2^(φ+1)   

Divide by 2:
φ^(2√2) 
2^(φ)

Let φ = √2+k, with k small. 
Let x=(√2+k)^(2√2)-2^(√2+k)

If k=0, then x=√2^(2√2)-2^(√2)=0

Any k larger than this will clearly yield a positive result, e.g. if k=(2-√2) then

(√2+2-√2)^(2√2)-2^(√2+2-√2) = 2^(2 √2) - 2^2, positive.

So expression I is larger than expression II

Edited on June 1, 2024, 11:09 am
  Posted by broll on 2024-06-01 11:08:15

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