If α,β and γ are the roots of the equation x3−3x2+3x+7=0, and ω is the cube root of unity, then the value of α−1β−1+β−1γ−1+γ−1α−1 is equal to
α, β, γ are the roots of x3−3x2 + 3x + 7 = 0(w is cube root of unity) then (α−1β−1+β−1γ−1+γ−1α−1) is