55. \(\dfrac{a-b}{a+b}+\dfrac{a+b}{a-b}\)

\[\frac{(a-b)^2+(a+b)^2}{(a+b)(a-b)}=\frac{a^2-2ab+b^2+a^2+2ab+b^2}{a^2-b^2}.\]

Ответ: \(\dfrac{2(a^2+b^2)}{a^2-b^2}\), \(a\ne\pm b\).