|3-2b|-|5b-2a|+|8b-1|-|3a+1|
因为b<0,a>0,|b|<|a|,
所以原式=3-2b+5b-2a+1-8b-3a-1
=-5b-5a+3
当a=2/3,b=-1/4时
代入算下=-5(2/3-1/4)+3
=-5×5/12+3
=11/12
|3-2b|-|5b-2a|+|8b-1|-|3a+1|
因为b<0,a>0,|b|<|a|,
所以原式=3-2b+5b-2a+1-8b-3a-1
=-5b-5a+3
当a=2/3,b=-1/4时
代入算下=-5(2/3-1/4)+3
=-5×5/12+3
=11/12