Question

помогите с заданием.​

Answer 1

$\dfrac{2}{d-1} -\dfrac{2}{d+1}=\dfrac{2(d+1)-2(d-1)}{(d-1)(d+1)}=\dfrac{2d+2-2d+2}{d^{2} -1}=\boxed{\dfrac{4}{d^{2}-1 }}\\\\\\d^{2} -1=-4\\\\\\\dfrac{4}{d^{2}-1 }=\dfrac{4}{-4}=-1\\\\\\Otvet:\boxed{-1}$