a^2-8a+b^2-2b+17=0
(a-4)^2+(b-1)^2=0
a=4,b=1
(根号a+b)÷根号(3b-根号a)
=(根号4+1)÷根号(3*1-根号4)
=(2+1)÷根号(3-2)
=3÷1
=1