∵（4a+1）²+|2b-a-¾|=0
∴4a+1=0,2b-a-¾=0
a=-1/4,b=1/4
4(3a-5b)-3(5a-7b+1)+(2a+7b-1)
=12a-20b-15a+21b-3+2a+7b-1
=-a+8b-4=1/4+2-4=-7/4