Equivalent to apply_matrix_pt(M, (p,q)) - apply_matrix_pt(M, (0,0))

def apply_matrix_norm(m, v):
    """Equivalent to apply_matrix_pt(M, (p,q)) - apply_matrix_pt(M, (0,0))"""
    (a, b, c, d, e, f) = m
    (p, q) = v
    return (a*p+c*q, b*p+d*q)