Answer
$\dfrac{2ab-b^2}{a^2-b^2}$
Work Step by Step
The expressions are not similar since they have different denominators.
To make the expressions similar, find the LCD (least common denominator) first. Factor each denominator to have:
$\\a^2-b^2=(a-b)(a+b)
\\a+b=a+b$
Thus, the LCD is $(a-b)(a+b)$.
Make the expressions similar using their LCD to have:
$\\=\dfrac{ab}{(a-b)(a+b)}+\dfrac{b(a-b)}{(a+b)(a-b)}
\\=\dfrac{ab}{(a-b)(a+b)}+\dfrac{ab-b^2}{(a-b)(a+b)}
\\=\dfrac{ab+ab-b^2}{(a-b)(a+b)}
\\=\dfrac{2ab-b^2}{(a-b)(a+b)}
\\=\dfrac{2ab-b^2}{a^2-b^2}$
