[tex]x^{6}+6x^{4}-m^{3}x^{3}+3(5-m^{2})x^{2}-6mx+10=0\\\Leftrightarrow x^{6}+6x^{4}-m^{3}x^{3}+15x^2-3m^2x^2-6mx+10=0\\\Leftrightarrow (x^6+6x^4+12x^2+8)+(-m^3x^3-3m^2x^2-3mx-1)+3x^2+3-3mx\\\Leftrightarrow (x^2+2)^3-(mx+1)^3+3(x^2-mx+1)=0\\\Leftrightarrow (x^2-mx+1)((x^2+2)^2+(x^2+2)(mx+1)+(m+1)^2+3)=0\\\Leftrightarrow x^2-mx+1=0(Do (x^2+2)^2+(x^2+2)(mx+1)+(m+1)^2+3>0)\\\Leftrightarrow m=\frac{x^2+1}{x}[/tex]
ĐK để PT có 2 nghiệm PB: [tex]\left[\begin{matrix} m>2\\m<-2 \end{matrix} \right.[/tex]
Đặt [tex]f(x)=\frac{x^2+1}{x}[/tex]
[tex]\Leftrightarrow f'(x)=1-\frac{1}{x^2}\\f'(x)=0\Leftrightarrow x= \pm 1[/tex]
Có BBT:

Vậy [tex]m\epsilon (2;\frac{5}{2}][/tex]
$T= 5.2 + 8.\frac{5}{2}=30$
Chọn C