z=6-x^2-y^2和z=根号下x²+y²

(y-z)^2+(z-x)^2+(x-y)^2=(x+y-2z)^2+(y+z-2x)^2+(z+x-2y)^2[(y-z)^2-(y+z-2x)^2]+[(z-x)^2-(x+z-2y)^2]+[(

2x+6y+z=73x+9y+z=8两式相减x+3y=1x=1-3y两式相加5x+15y+2z=155-15y+15y+2z=15z=5x+y+z=1-3y+y+5=6-2y得不到x+y+z=5的结论

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

一式和二式相加,可得3x+3y=15,即x+y=5……④一式和三式相加,可得4x+6y=24,即2x+3y=12……⑤⑤-2④可得y=2,所以x=3,代入一式,得z=1所以,方程组的解为x=3,y=2

x-7y+3z=17方程15x-6y-z=24方程23x+7y-2z=1方程3方程1变为x=17+7y-32z代入方程2和方程3得5(17+7y+32z)-6y-z=24方程43(17+7y+32z)

2x-3y-4z=01式x+y+z=02式1式+2式×4得到：2x-3y-4z+4x+4y+4z=06x+y=06x=-yx:y=(-1):61式-2式×2得到：2x-3y-4z-2x-2y-2z=0

亲,题目看似很麻烦,仔细想还是有思路的.解:由4x-3y-6z=0,(1式)x+2y-7z=0(2式)(2式)*4得:4x+8y-28z=0(3式)(3式)-(1式)得:4x+8y-28z-(4x-3

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

设a=x-y,b=y-z,-a-b=z-x(y-z)平方+(x-y)平方+(z-x)平方=(y+z-2x)平方+(z+x-2y)平方+(x+y-2z)平方b^2+a^2+(-a-b)^2=(-a-b-

这道题看似复杂,但是按步骤解就不难了.对于有绝对值的方程就一定要讨论了.x,y,z都有三种可能,x《-2,-2《x《3,x》3,y《-3,-3《y《1,y>1,z

(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)&

0和－2再答：0和－2再问：说清是X等于几和z等干几

5x+6y+2z=80和4x-3y+z=16两个方程化简求得13x+4z=1125x+6y+2z=80和3x-2y+6z=92两个方程化简求得14x+20z=356然后两个化简求得的方程求得x=4z=

=x²(y-z)+y²(z-x)+z²(x-z+z-y)=(y-z)(x²-z²)+(z-x)(y²-z²)=(y-z)(x-z)

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

括号是什么意思?只有一半

设x/2=y/3=z/5=ax=2ay=3az=5a是不是求的是：(x+3y-z)/(x-3y+z)?若是,如下：(x+3y-z)/(x-3y+z)=(2a+9a-5a)/(2a-9a+5a)=-3

根据公式(a+b+c)^2=a^2+b^2+c^2+2ab+2bc+2ac公式展开：得到(x^2+y^2+z^2=2xy-2yz-2xz)-(x^2+y^2+z^2-2xy-2yz+2xz)合并同类项