计算1.(x+y)(x-y)+(y-z)(y+z)+(z-x)(z+x) 2.（a+b-3)(a+b+3)

提公因式法（急!(x+y+z)(x-y+z)+(y-x+z)(y-x-z)和a(a-b-c)+b(c-a+b)+c(b- 计算:1:(2a-3b-c)^2 2:(3y-y-1)(y-3x-1) 3:(2x+y-z)(z-2x+y) 已知X+Y+Z=a,XY+YZ+XZ=b,求X*X+Y*Y+Z*Z的值 ）1.若2的a次方=3,2的b次方=6,求b-a的值.2.运用乘法公式计算（2x+y+z)(2x-y-z)+(y+z)& 已知x,y,z是三个非负数,并且满足3x+2y+z=5,2x+y-3z=1.设k=3x+y-7z,记a为k的最大值,b为 1.（x+y-z)+(x-y+z)-(x-y-z) 2.2x-(3x-2y+3)-(5y-2) 已知x+y+z=3,x平方+y平方+z平方=19,x立方+y立方+z立方=30,则a+b= 试证明(x+y-2z)+(y+z-2x)+(z+x-2y)=3(x+y-2z)(y+z-2x)(z+x-2y) (1) (a+2b/a-b)+(b/b-a)-(2a/a-b); (2) (y/x-y+z)+(2x+z/y-x-z)- (x+y-z)(x-y+z)= (a+2b-1)²与(2x+y+z)(2x-y-z)这两题请详解, 1.已知x,y,z∈R,且x+y+z=a 求证x^2+y^2+z^2≥(a^2)/3 2.已知a、b、c>0,a+b+c