X²+2XY+Y² (X + Y)² (X + Y)²
---------------- = ----------------------------------- = ------------------------------- =
X²-2XY-3Y² X²+2XY+Y² - 4XY - 4Y² (X + Y)² - 4Y(X + Y)
(X + Y)² X + Y
= ------------------------------- = ---------------
(X + Y)( X + Y - 4Y) X - 3Y