证明 y²z² z²x² x²y²≥xyz(x y z)

左-右,以xyz为分母进行通分,化简合并后,得分子：z(x-y)^2+x(y-z)^2+y(z-x)^2分母：xyz除成3个式子:(x-y)^2/xy+(y-z)^2/yz+(z-x)^2/xz利用x

1／x＝p1／y＝q1／z＝rpq+qr+pr=1(y+x)/z+(y+z)/x+(z+x)/y≥2(1/x+1/y+1/z)^2为(pq+qr+pr)[r/p+r/q+q/r+q/p+p/r+p/q

[x+(z-y)][x-(z-y)]=x-(z-y)记得采纳啊

∑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

【证明】首先必须了解和差化积公式sinα+sinβ=2sin[(α+β)/2]·cos[(α-β)/2]（1）sinα-sinβ=2cos[(α+β)/2]·sin[(α-β)/2]（2）cosα+c

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

(1)原式=x+y+z)(-x+y+z)(x-y+z)(x+y-z)=[(x+y+z)(x+y-z)]*{[z+(x-y)][z-(x-y)]}=[(x+y)^2-z^2][z^2-(x-y)^2]=

(x+y-z)(x-y+z)-(y+z-x)(z-x-y)=(x+y-z)(x-y+z)+(y+z-x)(x+y-z)所以公因式是(x+y-z)

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

如果可以用排序不等式证明的话x^2+y^2+z^2>=x^1.5y^0.5+y^1.5z^0.5+z^1.5x^0.5=2xxy/2(xy)^0.5+2yyz/2(yz)^0.5+2zzx/2(zx)

X--水平横向方向；Y--水平竖向方向；Z--垂直竖向方向.

这样来说明,按3分类,一个数被3除只可能余0,1,2三种情况,如果,xyz这三个数同余,那么x-y,y-z,x-z都是3的倍数,则乘积就是27的倍数,即x+y+z是27的倍数成立除此外,还有两种可能,

将(x+y+z)²展开有(x+y+z)²=x²+y²+z²+2xy+2xz+2yz=x²+y²+z²所以2xy+2xz+

假设x,y,z>0.那么由算数几何不等式推出sqrt[3]{xyz}=3*sqrt[3]{x/y/z*y/z/x*z/x/y}=3*sqrt[3]{1/xyz}.把(1)代入上式,就得到左边>=3*3

(x+y+z)^5-(x+y-z)^5-(x+z-y)^5-(z+y-x)^5=80xyz(x^2+y^2+z^2)注:x^5,y^5,z^5之类的是被消掉了.我的结果100%是正确的,你再算算吧.朝

X+Y+Z

x^4(y-z)+y^4(z-x)+z^4(x-y)=xy(x^3-y^3)+yz(y^3-z^3)+zx(z^3-x^3)=xy(x^3-y^3)+yz(y^3-z^3)-zx[(x^3-y^3)+

应用平方差公式a^2-b^2=(a+b)(a-b)(x+y+z)(x+y-z)(x-y+z)(-x+y+z)=[(x+y)^2-z^2][z^2-(x-y)^2]=-z^4+[(x+y)^2+(x-y

（x+y+z)(-x+y+z)(x-y+z)(x+y-z)=-[(x+y+z)(x+y-z)][(x-y+z)(x-y-z)]=-[(x+y)²-z²]*[(x-y)²-