[(x∨2+y∨2)-(x-y)∨2+2y(x-y)]÷4y+4=[x^2 + y^2 - x^2 + 2xy - y^2 +2xy - 2y^2]÷4y+4= (4xy-2y^2)/4y+4 = (2x - y)/2 +4因为2x - y = 18 所以 原式 = 18/2 +4 = 9 +4 = 13