Cho $\it{x}_{\,\it{i}}\in \left ( \,\it{0},\,\it{1}\, \right ]\,\,\left ( \it{i}= \overline{\it{1},\,\it{n}}\,,\,\,\it{n}\geqq \it{3} \right )$ . Chứng minh rằng :
$\left ( \it{1}- \prod\limits_{\it{i}= \it{1}}^{\it{n}}\,\it{x}_{\,\it{i}} \right )^{\,\it{n}}\geqq \prod\limits_{\it{i}= \it{1}}^{\it{n}}\,\left ( \it{1}- \prod\limits_{\it{j}\neq \it{i}}\,\it{x}_{\,\it{j}} \right )$
