求z=-5x-8y和z=-5x-8y的最大值,满足x+y

已知方程组3x+5y+3z=0,3x-5y-8z=0,并且z≠0,求x:z和y:z 求z=-5x-8y和z=-5x-8y的最大值,满足x+y 已知:x+y+z=0,5x-3y-z=0,求:5x-y+z/2x+8y+7z 的值 x/3=y/6=z/8 3x+5y-6z=-18 求x,y,z 已知x+y+yz=5,y+z+xy=8,x+z+xy=9,求x,y,z 已知x:y=3:6,y:z=8:5求x:y:z 已知x+7y+8z=3,3x-y+2z=5,求x+y+2z的值x+7y+8z=3,3x-y+2z=5是一个方程组 (y+z)/x=(z+x)/y=(x+y)/z求x+y-z/x+y+z的值 已知x、y、z是非负数,且满足条件:x+y+z=3,3x+y-z=5,求w=8x+4y+2z的最大值和最小值 已知方程组2x-y+z=5 5x+8y-z=9.求x+y的值. 已知方程组2x-y+z=5 5x+8y-z=-9.求x+y的值. 已知x-y/x+y=y+z/2(y-z)=z+x/3(z-x),求证8x+9y+5z=0THX.. 已知x/3=y/5=z/4,求x+y+z/y和x+y-z/y-x的值 已知x/3=y/5=z/4,求x+y+z/y和x+y-z/y-x的值,2种方法.急等. x+y-z=3 y+z-x=5 z+x-y=7 求x,y,z x/10 = y/8 =z/9 求x+2y+3z/y-5z (x*x+2)(y*y+4)(z*z+8)=64xyz,求x,y,z X+Y-Z=15 X+5Y+10Z=70 求：X、Y、Z