А(0,0,z) , B(3,3,1), С(4,1,2)
АВ=АС
АВ^2=AC^2
АВ^2=(3-0)^2+(3-0)^2+(1-z)^2
AC^2=(4-0)^2+(1-0)^2+(2-z)^2
(3-0)^2+(3-0)^2+(1-z)^2=(4-0)^2+(1-0)^2+(2-z)^2
Решаем уравнение
(2-z)^2-(1-z)^2=1
(2-z+1-z)*(2-z-1+z)=1
[b]z=1[/b]