Tìm tất cả các giá trị của m để y = x + 16/x + m đồng biến trên (0;16)

$$\eqalign{ & y = x + {{16} \over x} + m\,\,DB/\left( {0;16} \right) \cr & y' = 1 - {{16} \over {{x^2}}} = 0 \Leftrightarrow {{{x^2} - 16} \over {{x^2}}} = 0 \Leftrightarrow x = \pm 4 \cr & BXD: \cr & x\,\,\,\,\,\,\, - \infty \,\,\,\,\,\,\,\,\,\,\,\, - 4\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,4\,\,\,\,\,\,\,\,\,\,\,\, + \infty \cr & y'\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, + \,\,\,\,\,\,\,\,0\,\,\,\,\,\,\, - \,\,\,\,\,\,\,0\,\,\,\,\,\,\,\, + \cr & \Rightarrow Hs\,\,DB/\left( { - \infty ; - 4} \right);\,\,\left( {4; + \infty } \right) \cr & \Rightarrow Khong\,\,ton\,\,tai\,\,m\,\,de\,ham\,\,so\,\,DB/\left( {0;16} \right) \cr}$$