Over an algebraically closed field F of zero characteristic polynomial map ξ:Fn→Fn of the form ξ(x)=x−((xA1)3,(xA2)3,...,(xAn)3), where x=(x1,x2,...,xn) a row vector of variables, Ai∈Fn are column vectors, is considered. It is shown that if det(∂ξ(x))=1, then ξ is injective.