计算（2x+y-z+10)(2x-y+z+10)

(y-x)/(x+z-2y)(x+y-2z)+(z-y)(x-y)/(x+y-2z)(y+z-2x)+(x-z)(y-z x,y,z正整数 x>y>z证明 x^2x +y^2y+z^2z>x^(y+z)*y^(x+z)*z^(x+y) 协方差怎样计算?3个变量 X,Y,Z.Cov(Z,X) = 10,Cov(Z,Y) = 5A = 2X + Y - 1求 化简(y-x)(z-x)/(x-2y+z)(x+y-2z)+（z-y)(x-y)/(x-2z+y)(y+z-2x)+(x 三元一次方程组数学题x+2y+2z=33x+y-2z=72x+3y-2z=10x-y=2z-x=3y+z=-1x-y-z (4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=? kuai (x-2y+z)(x+y-2z)分之（y-x)(z-x) + (x+y-2z)(y+z-2x)分之(z-y)(x-y) x+2y+3z=10,x-y+4z=10,x+3y+2z=2 x-y+4z=10,x+3y+2z=2,x+2y+3z=11. x+y+z=4 2x+3y-z=6 3x+2y+2z=10 3x+2y+z=14 ,x+y+z=10,z+2x+3y=1 5 [3x+2y+z=14,x+y+z=10,2x+3y-z=1]