2y²/(xy + 2y²) - (2xy - x²)/(x² - 4y²) = 2yy/y(x + 2y) - x(2y - x)/(x - 2y)(x+2y) = 2y/(x + 2y) + x)/(x + 2y) = (x + 2y)/(x+2y) = 1
2y²/(xy + 2y²) - (2xy - x²)/(x² - 4y²) = 2yy/y(x + 2y) - x(2y - x)/(x - 2y)(x+2y) = 2y/(x + 2y) + x)/(x + 2y) = (x + 2y)/(x+2y) = 1