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Search options not deleted user 75701

for questions involving inequalities, upper and lower bounds.

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Lower bound for $ \sum_{i=1}^n x_i f(x_i)$ when $\sum_{i=1}^{n}x_i = K$

Actually,the conclusion is negative. By chebyshev's theorem, we have $$ \sum_{i=1}^{n}{x_{i}\cdot f(x_{i})}\geq \frac{\sum_{i}^{n}{f(x_{i} ) } }{n} \times \sum_{1}^{n}{x_{i} } $$ $$ \forall x_{1}< …
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