А) y^2(x+y)/y(x+y)(x-y)=y/(x-y)
б) (a^3/a^2)(a^2-b^2)/(4(a-b)=a(a+b)/4
в)(12ac^2/-b^6)(b^4/-18a^2c)=2b^2c/3a
а)(c-d)/c(c+d)-c/d(c+d)):(d^2/c(c^2-d^2)+1/(c+d))=
=(cd-d^2-c^2)/cd(c+d):(d^2+c^2-cd)/(c+d)=-1/cd
б)4(3-x)+5(x+3)/(9-x^2)-(4x+36)/9-x^2)=(12-4x+5x+15-4x-36)/(9-x^2)=(-3x-9)/(9-x^2)=-3(x+3)/(9-x^2)=3/(x-3)