Có :
P = 1 - 2/x + 2016/x^2
= (2016/x^2 - 2/x + 1/2016) + 2015/2016
= \(\left(\frac{\sqrt{2016}}{x}-\frac{1}{\sqrt{2016}}\right)\)^ 2 + 2015/2016 >= 2015/2016
Dấu "=" xảy ra <=> \(\frac{\sqrt{2016}}{x}-\frac{1}{\sqrt{2016}}=0\)<=> x=2016
Vậy ..............
Tk mk nha