R = rac(p+q)^2 + (p-q)^2(p-q)(p+q) - 2 = racp^2 + 2pq + q^2 + p^2 - 2pq + q^2p^2 - q^2 - 2 = rac2p^2 + 2q^2p^2 - q^2 - 2. - Portal da Acústica