Let $$\omega$$ be a complex cube root of unity with $$\omega$$ $$\ne$$ 1 and P = [p_ij] be a n $$\times$$ n matrix with p_ij = $$\omega$$^{i + j}. Then P² $$\ne$$ 0, when n = ?

The function $$f(x) = 2\left| x \right| + \left| {x + 2} \right| - \left| {\left| {x + 2} \right| - 2\left| x \right|} \right|$$ has a local minimum or a local maximum at x =