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Inegalitate integrala de tip Cauchy si cu derivata

Posted: Fri Mar 21, 2008 12:44 am
by Cezar Lupu
Fie \( f:[0,1]\to\mathbb{R} \) o functie de clasa \( C^{1} \) pe intervalul \( [0,1] \). Sa se demonstreze ca

\( \int_0^1f^{2}(x)dx-\left(\int_0^1f(x)dx\right)^{2}\leq \int_0^1|f^{\prime}(x)|dx\left(M-\int_0^1f(x)dx\right) \),

unde \( M=\sup_{x\in [0,1]}f(x) \).

Posted: Tue May 06, 2008 8:31 pm
by o.m.
:idea:


\( K=[0;1]^2 \)

LHS is equal

\( \frac{1}{2}\int\int_{K}(f(x)-f(y))^2dxdy \)

use this for the inequality and
\( f(x)-f(y)=\int_{y}^{x}f^{\prime}(t)dt \)