Phân tích đa thức

6, (x/xy-y^2 - x/x^2-xy). x^2y + xy^2/x^2-y^2
7, (1 + x/y + x^2/y^2)(x/y - 1).y^2/x^3-y^3
8, (a-b/a+b - a+b/a-b)(a^2+b^2/2ab + 1)
9, (a^2/b b^2/a)(a+b/a^2+ab+b^2 + 1/a-b)
10, (a/ab - 2a-b/a^2-ab): a^2-2ab+b^2/a^2b-ab^2