Спростіть вираз (a/b^2-ab+b/a^2-ab)*ab/b+a

(a/(b²-ab)+b/(a²-ab))*ab/(b+a)= (a/(b(b-a))+b/(a(a-b)))*ab/(b+a)= ((a²- b²)/ab(b-a))*ab/(b+a)= (-(a+b)/ab)*ab/(b+a)=-1