|a+b|+√（b-a)^2+|a|-|b|= |a+b|+|a-b|+|a|-|b|,
(|a+b|+|a-b|)^2=2[a^2+b^2+|a^2-b^2|],①
|a|>=|b|时①=4a^2,原式=3|a|-|b|;
|a|<|b|时①=4b^2,原式=|a|+|b|.