F(x)={{x}^{6}}\] and \[f(x)={{x}^{7}},\,\,f'(0)=f''(0)=f'''(0)\] \[={{f}^{iv}}(0)={{f}^{v}}(0)=0\]. \[x=0\] is point of MINIMA for \[f(x)={{x}^{6}}\]. But \[x=0\] is not point of maxima/minima for \[f(x)={{x}^{7}}\]. Hence, it is DIFFICULT to say anything.