因为,|3a-b+5| ≥ 0 ,(5a-7b+3)2 ≥ 0 ,所以,|3a-b+5|+(5a-7b+3)2 ≥ 0 ；要使 |3a-b+5|+(5a-7b+3)2 = 0 ,必须 |3a-b+5| = 0 ,(5a-7b+3)2 = 0 ；则有：3a-b+5 = 0 ,5a-7b+3 = 0 ；解得：a = -2 ,b = -1 ....