1.x+y/x-y · x-y/x+y=(x+y)(x-y) / (x+y)(x-y)=12.3a-3b/10ab · 25a^2b^3/a^2-b^2=15(a-b)a^2b^3 / 2(a+b)(a-b)ab=15ab^2/2(a+b)=15ab^2/(2a+2b)3.x^2-4y^2/x^2+2xy+y^2 ÷ x+2y/2x^2+2xy=(x+2y)(x-2y) / (x+y)^2 ...