4x-3y-6z=0 (1)x+2y-7z=0 (2)(1)*2+(2)*38x-12z+3x-21z=011x=33zx=3z(1)-(2)*4-3y-6z-8y+28z=0-11y=-22zy=2z(2xy+3yz-6zx)/(x^2+5y^2+7z^2)=(6z^2+6z^2-18z^2)/(9z^2+20z^2+7z^2)=-6z^2/36z^2=-1/6
确定题目正确么
