5y/y^2+3y-4 - y-1/y^2-1

5y - y - 1 = 5y (y² - 1) - (y - 1) (y² + 3y - 4) =

y² + 3y - 4 y² - 1 (y² + 3 - 4) (y² - 1) (y² + 3 - 4) (y² - 1)

5y³ - 5 - y³ + 3y² - 8y + 4 = 5y³ - y³ + 3y² - 8y - 5 - 4 = 4y³ + 3y² - 8y - 9

y^4 + 6y² + 1 y^4 + 6y² + 1 y^4 + 6y² + 1 y^4 + 6y² + 1

I think that the answer will be

5y/y^2+3y-4 - y-1/y^2-1

5/y+2y-5-1/y^2