x^2+2xy+y^2-(x^2-2xy+y^2)/x=x^2+2xy+y^2-x^2+2xy-y^2/x=4xy/x=4y
((x + y) ² - (x - y) ²) /х = ((х² + 2xy +y²) - (x² - 2xy +y²)) /x = (х² + 2xy +y² - x² + 2xy -y²) /x = 4xy / x = 4y
