[2x^2-4x+2 ] / (x-1)^3
=2(x^2-2x+1) / (x-1)^3
=2(x-1)^2 / (x-1)^3
=2 / (x-1)b^2-6ab+9a^2分之3a^2-ab(3a^2-ab ) / (b^2-6ab+9a^2) =a(3a-b) / (b-3a)²=a(3a-b) / (3a-b)²=a / (3a-b)