а) 9xy/2a^4b^3...
б) (a/(a+1)+1)...
в) ((x-y)/(x+y)...
б)1)(a+a+1)/(a+1)=(2a+1)/(a+1);
2) (1-(3a^(2)/(1-a^(2)))=(1-4a^(2))/(1-a^(2);
3)(2a+1)*(1-a^(2)/(a+1)*(1-4a^(2)=(1-a)/(1-2a).
в)1)((x-y)^(2)+(x+y)^(2))/(x+y)(x-y)=
=2(x^(2)+y^(2))/(x+y)(x-y);
2) (x^(2)+y^(2))/xy;
3) 2(x^(2)+y^(2))/(x+y)(x-y)* xy/(x^(2)+y^(2))=2xy/(x+y)(x-y).