(x^2-3x)/(x^2-6x+9)
=x(x-3)/(x-3)^2
=x/(x-3)
(4b-10a)/(25a^2-20ab+4b^2)
=2(2b-5a)/(5a-2b)^2
=2(2b-5a)/(2b-5a)^2
=2/(2b-5a)
(2a^2-8ab+8b^2)/(2a^2-8b^2)
=(a^2-4ab+4b^2)/(a^2-4b^2)
=(a-2b)^2/[(a-2b)(a+2b)]
=(a-2b)/(a+2b)