So sánh $2(|x| +|y|)$ & $|x+y| + |x-y|$.
So sánh $2(|x| +|y|)$ & $|x+y| + |x-y|$.
Started By cool hunter, 03-05-2012 - 21:27
#1
Posted 03-05-2012 - 21:27
Thà đừng yêu để giữ mình trong trắng
Lỡ yêu rôì nhất quyết phải thành công
#2
Posted 03-05-2012 - 21:49
$2(|x|+|y|)=|x|+|y|+|x|+|-y|\geq |x+y|+|x-y|$
$"=" \Leftrightarrow xy=0$
$"=" \Leftrightarrow xy=0$
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