|a-5|=8b-b^2-16
|a-5|+(b-4)^2=0
a-5=0,b-4=0
a=5,b=4
原式=5/根号(5*5*4)+根号(5*5*4)-4/5-(5+4)/根号(5*5*4)
=5/10+10-4/5-9/10
=10-4/5-2/5
=10-6/5
=8.8