4分之x=5分之y=6分之z,2x 3y-4z=-3-搜答案-搜搜考试网

令(X+Y)/5=(Y+Z)/6=(x+z)/7=k得x+y=5k①y+z=6k②z+x=7k③以上三式左右分别相加得2(x+y+z)=18kx+y+z=9k④④-②得x=3k④-③得y=2k④-①得

x=2y/3x=4y/32y/3+2y+4y/3=64y=6y=3/2x=1z=2

解方程组：x:y:z=2:3:4x+y+z=54解析：x:y:z=2:3:4＝＝》x:2=y:3=z:4,令x:2=y:3=z:4=a,所以x=2a,y=3a,z=4a,代入x+y+z=54,得到9a

设(x+y-z)/z=(x-y+z)/y=(-x+y+z)/x=k则（1）x+y-z=kz（2）x-y+z=ky（3）-x+y+z=kx（1）+（2）+（3）得x+y+z=k(x+y+z)∴k=1时,

解由5分之x=4分之y=3分之z令5分之x=4分之y=3分之z=k则x=5k,y=4k,z=3kk不等于0则3x-2y分之x+y+z=（3x-2y）分之（x+y+z）=（3*5k-2*4k）分之（5k

设：k=3分之x=4分之Y=6分之Z则：x=3k,y=4k,z=6kX-Y+Z分之X+Y-Z=(3k-4k+6k)/(2k+4k-6k)=5k/k=5

xy/(x+y)=51/x+1/y=1/5yz/(y+z)=7/21/y+1/z=2/7zx/(z+x)=41/x+1/z=1/4(xy+yz+zx)分之xyz=1/(1/x+1/y+1/z)=280

50/3

令(y+z)/x=(z+x)/y=(x+y)/z=ky+z=kxx+z=kyx+y=kz2(x+y+z)=k(x+y+z)2(x+y+z)=k(x+y+z)(2-k)(x+y+z)=0(x+y+z≠0

令a=x/3=y/4=z/5所以x=3ay=4az=5a所以3a-8a+15a=3010a=30a=3所以x=9,y=12,z=15

因为x/3=y/4=z/5所以可令x=3k,y=4k,z=5k.（k不为0）所以带入得：(3x-2y+z)/(x+y+z)=1/2再问：为什么等于1/2--嗯题是x+y+z/3x-2y+z.....不

∵x/4=y/5　∴x:y=4:5　∵y/5=z/3　∴y:z=5:3　∴x:y:z=4:5:3

由题意得y=三分之四x,z=三分之五x,代入上式约分后得(1+4/3)/(1+5-8/3)(x约去)=7/10=0.7

答案11分之14看图

令x/3=y/4=z/5=t则x=3t,y=4t,z=5t(x+2y+3z)/(2x+y-z)=(26t)/(5t)=26/5

x/4=y/4=z/5x=yz=5/4x(x+y)/(x-2y+3z)=(x+x)/(x-2x+3*5/4x)=2x/(11/4x)=8/11

x:y:z=3:4:5=6,求x-y+z分之x+y-z的值3y=4x,y=4x/3,3z=5x,z=5x/3x-y+z分之x+y-z=（x-4x/3+5x/3）/（x+4x/3-5x/3）=（4x/3

（1）x/3=y/4（2）y/4=z/5（3）x+y+z=24由（1）、（2）式化简成（4）、（5）（4）4x-3y=0（5）5y-4z=0由（4）得x=3y/4代入到（3）得（6）（6）3y/4+y

解:不防设x=2A,则y=3A,z=5A.由x+y+z=20,可知2A+3A+5A=20,10A=20,A=2.则x=4,y=6,z=10.