1) (4а^2 - 2a +1)/(8a^3+1) = (4а^2 - 2a +1)/(2a+1)(4a^2-2a+1)=1/(2a+1)
2) (2x+5)/(x-1) + 3/(x^2+2x+4) : (1-x)/(x^3-8) =
= (2x+5)/(x-1) + 3/(x^2+2x+4) : (1-x)/((x-2)(x^2+2x+4)) =
= (2x+5)/(x-1) + 3/(x^2+2x+4) * (x-2)(x^2+2x+4)/(1-x) =
= (2x+5)/(x-1) + (3*(x-2)/(1-x)) = (приводим к общему знаменателю (x-1), у второй дроби знаменатель (1-x) = - (x-1) ) = (2x+5-3(x-2))/(x-1) = (2x+5-3x=6)/(x-1) = (11 - x)/(x - 1)