1
а)3a/(3a-b)-a/(3a+b)-2ab/(3a-b)(3a+b)=(9a²+3ab-3a²+ab-2ab)/(3a-b)(3a+b)=
=(6a²+2ab)/(3a-b)(3a+b)=2a(3a+b_/(3a-b)(3a+b)=2a/(3a-b)
б)(9-6x)/(x-3)(x²+3x+9)+(3-x)/(x²+3x+9)=(9-6x+3x-9-x²+3x)/(x³-27)=-x²/(x³-27)=
=x²/(27-x³)
2
1)(y-4)²/(y²-4y+16):5(y-4)/(y+4)(y²-4y+16)=(y-4)²/(y²-4y+16)* (y+4)(y²-4y+16)/5(y-4)=
=(y²-16)/5
2)(y²-16)/5-(y²-20)/5=(y²-16-y²+20)/5=4/5