（3x+2y-5z+1）(-3x+2y-5z-1)

已知x:：y：z=3：4：5,(1)求x+y分之z的值；（2）若x+y+z=6,求x,y,z. 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/2=y/3=z/5 x+3y-z/x-3y+z 已知3x=4Y,5Y=6Z,求 (1)x:y:z;（2）x+y/y+z.请说明道理， （3x+2y-5z+1）(-3x+2y-5z-1) x²-y²+5x+3y+4（x+y-2xy)(x+y-z)+(xy-1）² {x+y+z=1;x+3y+7z=-1;z+5y+8z=-2 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 已知xyz≥0,x+y+z=1,化简x（2y-z）/(1+x+3y)+y(2z-x) /(1+y+3z) +z(2x-y)/(1+z+3x) 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) 已知实数x y z满足x/(x+1)=y/(y+2)=z/(z+3)=(x+y+z)/3,求x+y+z的值 已知实数x y z满足x/(x+1)=y/(y+2)=z/(z+3)=(x+y+z)/3,求x+y+z的值 已知x-y/x+y=y+z/2(y-z)=z+x/3(z-x),求证8x+9y+5z=0THX.. （2x-3y+z）-3{x-2【-z+（x-y）】-（3y-5z）} {x+y+z=1 x-2y+3z=5 2x-3y-3z=-8 2x-y+3z=3 {3X+Y-2Z=-1 X+Y+Z=5