z=6-x^2-y^2

x+2y-z=6①x-y+2z=3②，①×2+②，得x+y=5，则y=5-x③，①+2×②，得x+z=4，则z=4-x④，把③④代入x2+y2+z2得，x2+（5-x）2+（4-x）2=3x2-18x

实数x,y,z,满足那么x+y=6,z^2=xy-9,∴xy=z^+9,(x-y)^=(x+y)^-4xy=-4z^>=0,∴z=0,(x+y)^z=6^0=1.

（1）2x+3y-4z=-5（2）x+y+z=6（两边同时×33x+3y+3z=18（与（1）相减得（5）（3）x-y+3z=10（与（2）相加得（4））（4）2x+4z=16（5）x+7z=23（两

(5x+3y+2z)+(4x+6y+7z)=2011+20129(x+y+z)=4023x+y+z=447

{3x+y-z=4①,2x-y+3z=12②,x+y+z=6③}①+②得5x+2z=16④,②+③得3x+4z=18⑤④×2—⑤得7x=14,x=2所以z=3、y=1所以方程组的解为x=2、y=1、z

x+y-z=6y+z-x=2z+x-y=0三式相加得x+y+z=8-得2z=2z=1-得2x=6x=3-得2y=8y=4x=3y=4z=1

有这样的公式：a^3+b^3+c^2-3abc=(a+b+c)(a^2+b^2+c^2-ab-bc-ca)左边减右边,证明：（x+y-2z)^3+(y+z-2x)^3+(z+x-2y)^3-3（x+y

2x-y+2z=-17①3x+y-3z=-4②x+y+z=6③③*2：2x+2y+2z=12④④-①：3y=29y=29/3带入③：x+z=-11/3⑤带入②：3x-3z=-41/3即x-z=-41/

x+y+z-6=02x+3y-z-12=02x-y-z=0组成方程组再解x=2y=3z=1

1.x+y=16①y+z=12②z+x=10③①－②x-z=4④③＋④2x=14x=7⑤⑤代入①y=9⑥⑥代入②z=3x=7,y=9,z=3(2)3x-y+z=4①2x+3y-z=12②x+y+z=6

X+Y+Z=4,2*(X+Y+Z)+X=10,可以解出X=2.套入第二个和第一个.4+3Y-Z=66+2Y＋2Z＝10那么3Y=Z+2,2Y+2Z=4.Y=1,X=1X+Y+Z=4=2+1=12x+3

x+y+z=41式x+y+2z=52式3x+y-z=63式2-1式z=13-2式2x-3z=14式z=1代入4式x=2再代入1式y=1∴x=2,y=1,z=1请点击下面的【选为满意回答】按钮,再问：�

x+y+z=6(1)2x-y+z=3(2)3x+9y+z=24(3)(1)-(2)得：2y-x=3(4)(3)-(1)得：2x+8y=18即x+4y=9(5)(4)+(5)得：6y=12y=2代入(4

已知,2x+5y+4z=6,3x+y-7z=-4,可得：2(2x+5y+4z)+3(3x+y-7z)=2*6+3*(-4)=0；即有：13(x+y-z)=0,所以,x+y-z=0.

(x+y+z)²+(x-y-z)(x-y+z)-2·z(x+y)=(x+y)²+2z(x+y)+z²+(x-y)²-z²-2z(x+y)=(x+y)&

2x+y+z=2(1)x+2y+z=4(2)x+y+2z=6(3)(1)+(2)+(3)4x+4y+4z=12x+y+z=3(4)(1)-(4),x=-1(2)-(4),y=1(3)-(4),z=3

x=2y=3z=13x-y+z=42x+3y-z=12消z得5x+2y=162x+3y-z=12x+y+z=6消z得3x+4y=185x+2y=163x+4y=18合并得x=2y=3代入x+y+z=6

X+Y-Z=6.aY+Z-X=2.bZ+X-Y=0.ca,b,c三式相加X+Y+Z=8.dd式-a式2Z=2Z=1d式-b式2X=6X=3d式-C式2Y=8Y=4

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