已知（x-3）的2次方+（y+1）的2次方+z的2次方=0求x的2次方-2xy-5x的2次方+12xz+3xy

(x-3)^2+(y+1)^2+z^2=0
则
x-3=0
y+1=0
z=0
x=3
y=-1
z=0
x^2-2xy-5x^2+12xz+3xy-z^2-8xz-2x^2
=(x^2-5x^2-2x^2)-(2xy-3xy)+(12xz-8xz)-z^2
=-6x^2+xy+4xz-z^2
=-6*3^2+3*(-1)+4*3*0-0^2
=-54-3+0-0
=-57