Дробь: (x + x^2 + x^3) / (x^(-1) + x^(-2) + x^(-3)) / (-2)^2 == (x(1 + x + x^2)) / (1/x + 1/x^2 + 1/x^3) / 4 == (x^3 + x^4 + x^5)) / (x^3 + x^2 + 1) / 4 == (x^3(1 + x + x^2)) / (1 + x + x^2) / 4 == x^3 / 4.
Дробь: (x + x^2 + x^3) / (x^(-1) + x^(-2) + x^(-3)) / (-2)^2 =
= (x(1 + x + x^2)) / (1/x + 1/x^2 + 1/x^3) / 4 =
= (x^3 + x^4 + x^5)) / (x^3 + x^2 + 1) / 4 =
= (x^3(1 + x + x^2)) / (1 + x + x^2) / 4 =
= x^3 / 4.