Question

E(x)= (1/x +1/x la a doua + 1/x la a treia) : 1 + x + x la a doua/x la a patra - x la a treia. Demonstrati ca E(x)= x-1

Answer 1

E(x) = (1/x + 1/x^2 + 1/x^3): (1 + x + x^2) / (x^4 - x^3) =
        = [(x^2 + x + 1) / x^3] * {[x^3*(x-1)] / (x^2 + x + 1)}
        = x - 1.