(2x-3/5y-1/3z)(3/5y-1/3y+2x)帮忙哈!

1.（x+y-z)+(x-y+z)-(x-y-z) 2.2x-(3x-2y+3)-(5y-2) 2(x+y-z)-3(x-y+z)-5(x+y-z)+6(x-y+z) 计算 {x+y+z=1;x+3y+7z=-1;z+5y+8z=-2 x/2=y/3=z/5 x+3y-z/x-3y+z 方程组 (1) x+2y-3z=12 x-3y+2z= - 13 x-y-z=0 (2) x+ y=z 5x-y+z=18 2x+5y+3z= -1 x+Y+Z=1 X+3Y+7Z=-1 X+5Y+8Z=2x+Y+Z=1X+3Y+7Z=-1X+5Y+8Z=2 因式分解：25x y^2 z^2 (x+y-z)-30xyz(z-x-y)^2+5x y z^3 (z-x-y) 已知x-y/x+y=y+z/2(y-z)=z+x/3(z-x),求证8x+9y+5z=0THX.. {x+y+z=1 x-2y+3z=5 2x-3y-3z=-8 2x-y+3z=3 {3X+Y-2Z=-1 X+Y+Z=5 x+y+z=-5,3x+y+z=1,4x+3y+2z=-2快 已知x:y:z=1:3:5,求（2x+3y-z)/(x+y-2z)的值 3x+2y+z=14 ,x+y+z=10,z+2x+3y=1 5 x-y+z=-1 5x+2y-z=6 4x-3y+2z=-5 x+y+z=2 x-3y+2z=1 2x+2y+z+5 要具体步骤.. 3x-y+2z=-1 4x+y+z=5 x-2y-z=-2 {x+y+z=1 {x+3y+7z=-1 {x+5y+8z=2 x+y+z=-1 4x-2y+3z=5 y-z=8-2x