А)x/x-4 - x+2/x-2 = x(x-2)-(x+2)(x-4) / (x-4)(x-2)=x^2-2x-x^2+4x-2x+8 /(x-4)(x-2)=
=8 /(x-4)(x-2)
б)6y+ 12y/6y-1 -1 = 6y(6y-1)+12y-(6y-1) / (6y-1) =36y^2-6y+12y-6y+1/ (6y-1)=
=36y^2 +1/(6y-1)
в)a/3a-9b - 3b^2/a^2-3ab = a*a - 3b^2*3 /3a(a-3b)=a^2-9b^2 /3a(a-3b) =
= (a+3b)(a-3b) / 3a(a-3b) = a+3b / 3a