Let's simplify the expression step by step:

A - b/ sqr(a) - sqr(b) - a - sqr(ab)/sqr(a) - sqr(b)

First, simplify the numerator: A-b.

Next, simplify the denominator: sqr(a) - sqr(b) - a - sqr(ab).

Now rewrite the expression with the simplified numerator and denominator: (A-b) / (sqr(a) - sqr(b) - a - sqr(ab))

Finally, there is no further simplification possible without specific values for A and b.