16) \(\dfrac{(y+1)(y-1)}{-y-1}=\)

Так как \(-y-1=-(y+1)\), получаем:

\(\dfrac{(y+1)(y-1)}{-y-1}=\dfrac{(y+1)(y-1)}{-(y+1)}=-(y-1)=1-y\).

Ответ: \(1-y\), при \(y\ne-1\).