1.
x^2 + y^2 +z^2 = (x + y+ z) ^2 - 2*( xy+yz+xz) = 8
2.
配方
(x-1)^2 + (y+2)^2 + (z-3)^2 =0
x =1
y =-2
z = 3
x+y+z = 2兄弟我敬佩你，如果你能帮我把作业全做完我给你100财富撒