两个数差的绝对值大于等于这两个数绝对值差的绝对值

(|a-b|)^2-(||a|-|b||)^2=(a-b)^2-(|a|-|b|)^2=a^2-2ab+b^2-(|a|)^2+2|ab|-(|b|)^2=(|a|)^2-2ab+(|b|)^2-(|a|)^2+2|ab|-(|b|)^2=2(|ab|-ab)ab>=0时,|ab|-ab=0ab0综上,(|a-b|)^2-(||a|-|b||)^2>=0(|a-b|)^2-(||a|-|b|...