упростите выражение и найдите его значение при y=3

(y-2) / (y^2-1) - (y-1) / (y^2+y) = (y-2) / (y-1) (y+1) - (y-1) / y (y+1) =

[ (y (y+1) (y-2) - (y-1) (y-1) (y+1) ]/y (y-1) (y+1) = (y+1) (y (y+1) - (y-1) ^2) / (y (y+1) (y-1) =

= (y+1) (y^2-2y-y^2+2y-1) / y (y-1) (y+1) = (y+1) / y (y+1) (y-1) = 1/y (y-1)

при у=3 получим 1/6