А) x^2-xy / x^2-y^2=x(x-y) / (x-y)(x+y)=x / x+y
б)5y^2-5 / 3y^2-6y+3= 5(y^2-1) / (y-1)=5(y-1)(y+1) / (y-1)= 5y+5
в)=(2x-3y^2)^2 / 5(3y-2x)=-(3y-2x)(2x-3y) / 5(3y-2x)= -(2x-3y) / 5=3y-2x / 5
г)(mn-3n)+(3-m) / (m-3)(m+3)=n(m-3)+(3-m) / (m-3)(m+3)= 3-m / m+3