Question 625845
[(1/a)-(1/b)] / [(1/a^2)-(1/b^2)]= 

=  [(b-a)/ab]/[(b^2-a^2)/a^2b^2]

= [(b-a)/ab]a^2b^2/(b-a)(b+a)

= ab/a+b


Answer: d) ab/(a+b)