MF_(1)=sqrt(x^2+(y+5)^2+z^2)
MF_(2)=sqrt(x^2+(y-5)^2+z^2)
|MF_(1)-MF_(2)|=|sqrt(x^2+(y+5)^2+z^2)-sqrt(x^2+(y-5)^2+z^2)|
По условию
|MF_(1)-MF_(2)|=6
|sqrt(x^2+(y+5)^2+z^2)-sqrt(x^2+(y-5)^2+z^2)|=6
Возводим в квадрат
x^2+(y+5)^2+z^2 - 2sqrt(x^2+(y+5)^2+z^2)*sqrt(x^2+(y-5)^2+z^2)+x^2+(y-5)^2+z^2=36
или
2x^2+2y^2+2z^2+14=2sqrt(x^2+(y+5)^2+z^2)*sqrt(x^2+(y-5)^2+z^2)
или
x^2+y^2+z^2+7=sqrt(x^2+(y+5)^2+z^2)*sqrt(x^2+(y-5)^2+z^2)
(x^2+y^2+z^2+7)^2=(x^2+(y+5)^2+z^2)*(x^2+(y-5)^2+z^2)
(x^2+y^2+z^2)^2+14(x^2+y^2+z^2)+49=
=x^4+x^2y^2-10x^2y+25x^2+x^2z^2+
+x^2y^2+10x^2y+25x^2+y^4-50y^2+625+
z^2y+10z^2y+25z^2+z^2x^2+z^2y^2-10z^2y+25z^2+z^4
x^4+y^4+z^4+2x^2y^2+2x^2z^2+2y^2z^2+14(x^2+y^2+z^2)+49=
x^4+y^4+z^4+2x^2y^2+2x^2z^2+2y^2z^2+50(x^2+-y^2+z^2)
36x^2-64y^2+36z^2+576=0
9x^2-16y^2+9z^2+144=0
О т в е т.
Двуполостный гиперболоид
(x^2/16)-(y^2/9)+(z^2/16)= - 1