Proving a logarithmic inequality I'm interested why this is true: Considering AA (x,y,z) in (1,oo) The following holds: log_xy^z+ log_x(z^y)+log_y(z^x) >= 3/2

Widersinnby7

Widersinnby7

Answered question

2022-11-19

Proving a logarithmic inequality
I'm interested why this is true:
Considering  ( x , y , z ) ( 1 , )
The following holds:
log x y z + log x z y + l o g y z x 3 2
This is taken from a high school textbook of mine. I tried finding a meaningful manipulation by using AM-GM, but that got pretty messy. I'd like to avoid Lagrange multipliers since this is meant to be a pretty basic problem.
Any progress would be appreciated.

Answer & Explanation

Envetenib8ne

Envetenib8ne

Beginner2022-11-20Added 17 answers

CW answer to remove it from unanswered queue:
For ( x , y , z ) = ( 1.1 , 1.01 , 1.001 ), the expression is clearly 0.22 < 3 2 , contradicting the inequality at hand.
Layton Park

Layton Park

Beginner2022-11-21Added 3 answers

Hint
Set
f ( x , y , z ) = z ln y ln x + y ln z ln x + x ln z ln y
look at the stationary point and conclude.

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