AM=sqrt((0-8)^2+(y-4)^2+(0-(-2))^2)
BM=sqrt(0-(-2))^2+(y-6)^2+(0-4)^2)
АМ=ВМ
Приравниваем
sqrt((0-8)^2+(y-4)^2+(0-(-2))^2)=sqrt((0-(-2))^2+(y-6)^2+(0-4)^2)
Возводим в квадрат:
(0-8)^2+(y-4)^2+(0-(-2))^2=(0-(-2))^2+(y-6)^2+(0-4)^2
Находим y
(y-6)^2-(y-4)^2=60
(y-6-y+4)*(y-6+y-4)=60
-2*(2y-10)=60
2y-10=-30
2y=-20
y=-10
О т в е т. (0;-10;0)