已知3x-4y-z=0 2x+y-8z =0,求(x²+y²-z²)/(xy+yz)的值

来源：学生作业帮助网编辑：六六作业网时间：2024/11/25 23:45:18

已知3x-4y-z=02x+y-8z=0,求(x²+y²-z²)/(xy+yz)的值已知3x-4y-z=02x+y-8z=0,求(x²+y²-z

已知3x-4y-z=0 2x+y-8z =0,求(x²+y²-z²)/(xy+yz)的值
已知3x-4y-z=0 2x+y-8z =0,求(x²+y²-z²)/(xy+yz)的值

已知3x-4y-z=0 2x+y-8z =0,求(x²+y²-z²)/(xy+yz)的值
6x-8y-2z=0
6x+3y-24z=0
11y-22z=0
y=2z
3x-4(2z)-z=0
x=3z
(x²+y²-z²)/(xy+yz)=[(3z)^2+(2z)^2-z^2]/[(3z)+z](2z)=3/2

由3x-4y-z=0得z=3x-4y ③
由2x+y-8z=0得y=8z-2x ④
④代入③得
x=3z
y=2z
将x=3z,y=2z代入得
(x²+y²-z²)/(xy+yz)
=(9z²+4z²-z²)/(6z²+2z²)
=12z²/8z²
=12/8
=3/2

知3x-4y-z=0
2x+y-8z =0,
把z看成已知数，解得x=3z，y=2z
求(x²+y²-z²)/(xy+yz)的值
代入则
= (9z²+4z²-z²)/ (6z²+2z²)
= 12 / 8
= 3/2x和y是怎么具体得出的，可以再详细点...

全部展开

知3x-4y-z=0
2x+y-8z =0,
把z看成已知数，解得x=3z，y=2z
求(x²+y²-z²)/(xy+yz)的值
代入则
= (9z²+4z²-z²)/ (6z²+2z²)
= 12 / 8
= 3/2

收起

用一个字母表示另外两个字母。
3X-4Y=Z
2X+Y=8Z，
解得：X=3Z，Y=2Z，
∴(x²+y²-z²)/(xy+yz)
=(9Z²+4Z²-z²)/(6Z²+2z²)
=12/8
=3/2。

已知x-y/x+y=y+z/2(y-z)=z+x/3(z-x),求证8x+9y+5z=0THX.. 已知4x-3y+z=0,x+2y-8z=0,xyz不等于0,求x+y-z/x-y+2z的值已知3x-4y-z=0,2x+y-8z=0,且z≠0,则x：y：z=（）已知{x-3y+2z=0 3x-3y-4z+0,则x:y:z=? 已知x-2y+3z=0,x-3y+4z=0,则x:y:z= 已知2x-y-z=0,3x+4y-2z=0,则x：y：z=? 已知x+4y-3z=0,4x-5y+2z=0,则x：y：z 已知{x-5y+2z=0 3x-5y-4z=0,求x：y:z 已知方程组4x-5y+2z=0 x+2y=3z 则x:y:z 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 已知：4x-5y+2z=0 x+4y-3z=0则：(x*x+y*y+z*z)/(x*y+y*z+z*x)=____. 已知：x^2/(z+y)+y^2/(x+z)+z^2/(x+y)=0,求x/(z+y)+y/(x+z)+z/(x+y)的值. 已知(x+y)(x+z)=x,(y+z)(y+x)=2y,(z+x)(z+y)=3z,求x,y,z 已知方程组4x-3y-2z=0,x-3y+z=0,z≠0求x/z,y/z的值三元一次方程组题目x+y-z=11 y+z-x=5 x-y+z=1x+y=4 y+z=3 x+z=5若已知x-3y+2z=0 2x+3y-8z=0, 且xyz≠0,则x:y:z= 已知x+2y-4z=0,3x-y-z=0,则3x+2y+z/x+2y+z= 已知4x-3y-6z=0,x+2y-7z=0,求5x+2y-z/2x-3y-10z 已知4X-3y-3z=0 X-3y-Z=0求3X-2Z+Y/-x+y+Z的值