已知(x-3)^2+(y+1)^2+z^2=0,求x^2-2xy-5x^2+12xz+3xy-z^2-8xz-2x^2的值

问题描述:

已知(x-3)^2+(y+1)^2+z^2=0,求x^2-2xy-5x^2+12xz+3xy-z^2-8xz-2x^2的值

(x-3)^2+(y+1)^2+z^2=0

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