Since the Weyl group acts by reflections, they are isometries and so the degree 2 polynomial  is Weyl-invariant.
sˈɪns ðə wˈeɪl ɡɹˈuːp ˈækts baɪ ɹᵻflˈɛkʃənz, ðeɪ ɑːɹ aɪsˈɑːmətɹiz ænd sˌoʊ ðə dᵻɡɹˈiː tˈuː pˌɑːlɪnˈoʊmɪəl ɪz wˈeɪlɪnvˈɛɹiənt.