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x/3十y/4十7z=100,x十y十z=1oo求xyz值

解:4y + 100=1.2y + 56.4 4y - 1.2y=56.4 - 100 2.8y=-43.6 y=-109/7

x+1/y=4..........(1) y+1/z=1.........(2) z+1/x=7/3....(3) (1): 1/y=4-x y=1/(4-x).......(4) 代入(2): 1/(4-x)+1/z=1 1/z=1-1/(4-x) =(3-x)/(4-x) z=(4-x)/(3-x)........(5) (5)代入(3): (4-x)/(3-x)+1/x=7/3 [x(4-x)+(3-x)]/[x(3-x)]=7/...

x:y:z=2:3:4,x=2k,y=3k,z=4k x+y+z=1/12,2k+3k+4k=1/12,9k=1/12,k=1/108 x=2/108=1/54 y=3/108=1/36 z=4/108=1/27

X+1/Y=4 Y+1/Z=1 Z+1/X=7/3 消元后得到二元二次方程组,解得: X=3/2,Y=2/5,Z=5/3 所以XYZ=1 方程解起来挺烦得,我解了好一会而,要有耐心哦 解法二 (X+1/Y)(Z+1/X)(Y+1/Z)=XYZ+1/(XYZ)+X+Y+Z+1/X+1/Y+1/Z=XYZ+1/(XYZ)+4+1+7/3=4*1*7/3 得到:...

你好 这是个二元一次方程 (Y一6)x(X十3)=(Y十4)x(X一1), XY+3Y-6X-18=XY-Y+4X-4 4Y-10X-14=0 2Y-5X-7=0 只能化到这里 【数学辅导团】为您解答,不理解请追问,理解请及时选为满意回答!(*^__^*)谢谢!

利用小学知识吧 4/5=1/5+3/5=1/5+6/10=1/5+1/10+5/10=1/5+1/10+1/2 所以xyz=5*10*2=100

5分之168

解: 1/x+1/(y+z)=1/2, (x+y+z)/[x(y+z)]=1/2 即 1/x =(y+z)/[2(x+y+z)] 同样可得: 1/y=(x+z)/[3(x+y+z)] 1/z=(x+y)/[4(x+y+z)] 所以: 2/x+3/y+4/z =(y+z)/(x+y+z)+(x+z)/(x+y+z)+(x+y)/(x+y+z) =2(x+y+z)/(x+y+z) =2

从1/x+1/(y+z)=1/2, 可得 (x+y+z)/[x(y+z)]=1/2 即 1/x =(y+z)/[2(x+y+z)] 同样可得: 1/y=(x+z)/[3(x+y+z)] 1/z=(x+y)/[4(x+y+z)] 所以: 2/x+3/y+4/z =(y+z)/(x+y+z)+(x+z)/(x+y+z)+(x+y)/(x+y+z) =2(x+y+z)/(x+y+z) =2

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