2x+y+3z＝2 ﹣2x+3y+2z＝﹣3 4x+2y+9z＝1

1.x+y+z2.-x-3y-1

∑是循环和例如∑a=a+b+c∑a^2=a^2+b^2+c^2∑(z-y)(x-y)/(x+y-2z)(y+z-2x)＝∑(z-y)(x-y)(x+z-2y)/(x+y-2z)(y+z-2x)(x+z

(4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=4x-2y-z-5x[6y-(x+y)]+x-(3y-10z)=4x-2y-z-30xy+5x²+5xy+x-3

我去,这什么题啊

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

方程（1）+（2）得：3x-z=9④，方程（2）+（3）得：2x-z=7⑤，④-⑤得：x=2，把它代入⑤得：z=-3，把它代入（1）得：y=-3，∴原方程的解为x＝2y＝−3z＝−3．

∵x-2y+z=（x-y）-（y-z）,x+y-2z=（y-z）-（z-x）,y+z-2x=（z-x）-（x-y）．设x-y=a,y-z=b,z-x=c,则原式=-ac/(a-b)(b-c)+(-ba

正整数?取对数即证：2xlnx+2ylny+2zlnz>(y+z)lnx+(x+z)lny+(x+y)lnzx>y>z,lnx>lny>lnz由排序不等式得xlnx+ylny+zlnz>ylnx+zl

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

楼主好,4x-9z＝17.A3x+y+15z＝18.Bx+2y+3z＝2.C3C->3x+6y+9z=6.DA+D得：7x+6y+0Z=23.E5C->5x+10y+15z=10.FF-B得：2x+9

1、隐函数对x求导得1+az/ax+yz+xy*az/ax=0,故az/ax=－(1+yz)/(1+xy)；F对x求导得aF/ax=e^x*y*z^2+e^x*y*2z*az/ax；当x＝0,y＝1时

若a+b+c=0,可证a^3+b^3+c^3-3abc=a^3+b^3+(-a-b)^3-3ab(-a-b)=a^3+b^3+3ab(a+b)-(a+b)^3=(a+b)^3-(a+b)^3令a=x+

①x+2y-4z＝0②3x+y-z＝0①-2②x-6x-4z+2z=05x=2z代入①z=5x/2x+2y-10x=02y=9xy=9x/2x:y:z=1:9/2:5/2=2:9:5

x+2y=32y=3zx-y=-1x+2y=3①2y=3z②x-y=-1③①-③得3y=4,得y=4/3代入③,得x=y-1=1/3代入②,得z=2/3y=8/9x+y+z=36x-y=12x+z-y

2x+y+3z＝38①3x+2y+4z＝56②4x+y+5z＝66③③-①得：2x+2z=28，即x+z=14④，①×2-②得：x+2z=20⑤，由④和⑤组成方程组：x+z＝14x+2z＝20，解得：

25xy^2z^2(x+y-z)-30xyz(z-x-y)^2+5xyz^3(z-x-y)=25xy^2z^2(x+y-z)+30xyz(x+y-z)^2-5xyz^3(x+y-z)=5xyz(x+y

x+2y+3z＝1            ①2x+3y+z＝2 &nb

3元一次方程,好像是初一的问题哦.根据前面两个等式可以得出x=3zy=z(平方)/32x+3y+4z=2*(3z)+3*(z方/3)+4z现在变成了一元二次方程,你应该会解吧.

3x-2y-[-4x+(z+3y)]=3x-2y-(-4x+z+3y)=3x-2y+4x-z-3y=7x-5y-z

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