x=2.8,y=-4 1/5,z=-1 4/5,求-x-y+|-z|的值.

已知 x/(y+z)+y/(z+x)+z/(x+y)=1求 (x*x)/(y+z)+(y*y)/(x+z)+(z*z)/(x+y)=? {x+y-z=11 y+z-x=5 z+x-y=1 {x+y-z=11,x-y-z=-5,x-y+z=1 5x+y+z=1 2x-y+2z=1 x+5y-z=4 解方程x-y+4z=5,y-z+4x=-1,z-x-4y=4 x-y+z=-1 5x+2y-z=6 4x-3y+2z=-5 3x-y+2z=-1 4x+y+z=5 x-2y-z=-2 x+y+z=-1 4x-2y+3z=5 y-z=8-2x x+y+z=1 4x+5y-z=6 x+2y-z=3 x+y+z=-5,3x+y+z=1,4x+3y+2z=-2快 {x+y+z=1 {x+3y+7z=2 {x+5y+19z=4 1.{x:y:z=3:4:5 2x+3y-5z=-142.{x-y-z=-1 3x+5y+7z=11 4x-y+2z=-13.{x+y=1 x+z=0 2x+y+2z=44.{x-y+z=-3 2x-y-z=-2 -3x+y+z=-15.{x-y+z=-3 3x+y-4z=6 2x+y-z=36.{x-2y+5z=16 2x+y-5z=7 2x-y+z=38 x-y-z=-1 3x+5y+7z=11 4x-y+2z=-1 分别求出x=?y=?z=? 三元一次方程 X-y-z=-1 3x+5y+7z=11 4x-y+2z=-1 X=?Y=?Z=? 三元一次方程组{5x+y+z=1 2x-y+2z=1 x+5y-z=4 求X Y Z的值 x,y,z属于正实数,且3x+4y+5z=1 求1/(x+y)+1/(y+z)+1/(x+z)的最小值 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. x+2y-z=-5 x+y+2z=-1 3x+4y-2z=-12x+2y-z=3 2x+y+3z=0 4x+z=-4