Do I have correct plane equation?

[Halsafar]

Is this correct? did I expand it correctly?

    m_vNormal.x = P1.y * (P2.z - P3.z) + P2.y * (P3.z - P1.z) + P3.y * (P1.z - P2.z);
    m_vNormal.y = P1.z * (P2.x - P3.x) + P2.z * (P3.x - P1.x) + P3.z * (P1.x - P2.x);
    m_vNormal.z = P1.x * (P2.y - P3.y) + P2.x * (P3.y - P1.y) + P3.x * (P1.y - P2.y);
    m_fDistance = P1.x * (P2.y * P3.z - P3.y * P2.z) + P2.x * (P3.y * P1.z - P1.y * P3.z) + P3.x * (P1.y * P2.z - P2.y * P1.z);