a^2-4a+9b^2+6b+5=0
a^2-4a+4+9b^2+6b+1=0
(a-2)^2+(3b+1)^2=0
(a-2)^2=0,(3b+1)^2=0
a=2
b=-1/3
(a-b)/ab
=[2-(-1/3)]/(-1/3*2)
=(7/3)/(-2/3)
=-7/2
a^2-4a+9b^2+6b+5=0
a^2-4a+4+9b^2+6b+1=0
(a-2)^2+(3b+1)^2=0
(a-2)^2=0,(3b+1)^2=0
a=2
b=-1/3
(a-b)/ab
=[2-(-1/3)]/(-1/3*2)
=(7/3)/(-2/3)
=-7/2