判别下面两个齐次线性方程组是否有非零解,为什么?1 x+y+z=0,2x+y+5z=0 2 x+y+z=0,2x+y+5

当a,b取何值时,齐次线性方程组：{ax+y+z=0；x+by+z=0；x+2by+z=0有非零解 已知3x-2y-5z=0,2x-5y+4z=0,且x,y,z均不为0,求3x*x+2y*y+5z*z/5x*x+y*y- 已知(x+y+z)^2=x^2+y^2+z^2,证明x(y+z)+y(z+x)+z(x+y)=0 已知x、y、z满足方程组：x+y-z=6；y+z-x=2；z+x-y=0 求x、y、z的值 已知x,y,z 大于0,x+y+z=2,求证 xz/y(y+z)+zy/x(x+y)+yx/z(z+x)大于等于2/3 线性方程组2x-z=-1x+2y=0y+z=2即为2x+0×y-z=-1 2x+5y+4z=0,3x+y-7z=0,则x+y-z=? x+y-z=0 2x-3y+2z=5 x+2y-z=3 已知方程组4x-5y+2z=0 x+2y=3z 则x:y:z 已知x+y-z=0,2x-y+2z=0 求（3x-2y+5z)/(5x-3y+2z)的值 已知x+y-7z=0 x-2y+5z=0(xyz不等于0）,求x+2y-z/y-2x+12z 已知2x+2y-4z=0,2x+4y+5z=0,求x+y+z/x-y+z的值