Inegalitate logaritmica

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mihai++
Bernoulli
Posts: 206
Joined: Wed Nov 28, 2007 8:08 pm
Location: Focsani

Inegalitate logaritmica

Post by mihai++ »

Fie \( a,b,c\in(0,\infty),a+b+c=1 \).
Demonstrati ca: \( \log_a(a^2+b^2+c^2)+\log_b(a^2+b^2+c^2)+\log_c(a^2+b^2+c^2)\leq a\log_a(abc)+b\log_b(abc)+c\log_c(abc) \).


Va rog sa imi spuneti daca solutia mea e corecta:
\( a+b+c=1\Rightarrow a,b,c\in(0,1). \)
\( \sum \log_a(a^2+b^2+c^2)\leq\sum \log_a\frac{(a+b+c)^2}{3}=\sum \log_a\frac{1}{3}=(a+b+c)(\log_a\frac{1}{3}+\log_b\frac{1}{3}+\log_b\frac{1}{3})\leq\sum 3a\log_a\frac{1}{3}=\sum a\log_a(\frac{a+b+c}{3})^3\leq\sum a\log_a(abc). \)
Am aplicat medii si Cebasev.
n-ar fi rau sa fie bine :)
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