(b^4-a^2b^2)/(b^2*b-a))=b^2(b^2-a^2)/(b^2(b-a))=(b^2-a^2)/(b-a)=(b+a)(b-a)/(b-a)=b+a =5-sqrt(3)-7-sqrt(3)=2-2sqrt(3)
(b^4-a^2b^2)/(b^2*b-a))=b^2(b^2-a^2)/(b^2(b-a))=(b^2-a^2)/(b-a)=(b+a)(b-a)/(b-a)=b+a =5-sqrt(3)-7-sqrt(3)=2-2sqrt(3)