求证|a/b|+|b/c|+|c/d|+|d/a|amp;gt;=4
|a/b|+|b/c|+|c/d|+|d/a|=4 * 根号(|a/b|*|b/c|*|c/d|*|d/a|)=4 * 1 =4
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|a/b|+|b/c|+|c/d|+|d/a|=4 * 根号(|a/b|*|b/c|*|c/d|*|d/a|)=4 * 1 =4