1+b^(3/4) / 1-b^(1/4)+b^(1/2) - 2b^(1/8)
=(1+b^(1/4))*(1-b^(1/4)+b^(1/2))
Сокращаем и числитель и знаменатель дроби на (1-b^(1/4)+b^(1/2))
(1+b^(3/4))/(1-b^(1/4)+b^(1/2)) -2b^(1/8) =1+b^(1/4)-2b^(1/8)=
=(1-2b^(1/8)+(b^(1/8))^2)=(1-b^(1/8))^2