67. \(\dfrac{4y}{y^2-x^2}-\dfrac{2}{y-x}\)

Разложим \(y^2-x^2=(y-x)(y+x)\): \(\dfrac{4y-2(y+x)}{y^2-x^2}=\dfrac{2(y-x)}{(y-x)(y+x)}=\dfrac{2}{y+x}\).

Ответ: \(\dfrac{2}{y+x}\), где \(y\ne\pm x\).