(a+b):(a-b)=7:3
∴7(a-b)=3(a+b)
7a-7b=3a+3b
4a=10b
∴a/b=5/2
a=5/2b
ab+b2/a2+b2
=(5/2b²+b²)/(25/4b²+b²)
=14/29