4) Let g(x) = 5 4x4 + x^cos, x#0, 0, x = 0. where g: RR. Show that g has an absolute minimum at x = 0, but that its derivative has both positive and negative values in every neighborhood of 0. 5) Let f(x) = e¯ ½ for x # 0 and f(0) = 0 for x Є R. Show that the derivative off exists and is continuous on R with f'(0) = 0.