a=3.5,b=-0.8,则
6-5a0 8b-1>0
于是
丨6—5a丨—丨3a-2b丨-丨8b-1丨
=-(6-5a)-(3a-2b)-(8b-1)
=5a-6-3a+2b-8b+1
=2a-6b-5
=2×3.5-6×(0.8)-5
=7-4.8-5
=-2.8