1.x+y+z=26x-y=12x-z+y=182.4x+5y+2z=40x:y:z=1:2:33.x+y+z=1x+3y+7z=2x+5y+19z=44.x-y-z=2y-z-x=-5z-x-y=45.5x+4y+z+16=03x+y-4z=7x+y+z+6=06.5x+3y=4a6x-2y=9a4x-5y=8a-3都要用代入法!【最后一题除外】（就因为这才要求助什么的……）

(x+y-z)(x-y+z)= X+Y+Z=? x/y=(x+z)/(y+z)y/z=(x+y)/(x+z) 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)=? (y+z)/x=(z+x)/y=(x+y)/z求x+y-z/x+y+z的值 解方程 x(x+y+z)=6 y(x+y+z)=12 z(x+y+z)=18 解方程组{x(x+y+z)=6,y(x+y+z)=12,z(x+y+z)=18 z+=x>y?++x: x+y=8 y+z=12 x+z=10 x+y+z= x+y=8 y+z=12 x+z=10 x+y+z= X+Y+Z=26X-Y=12X-Y+Z=18 用行列式的性质证明：y+z z+x x+y x y z x+y y+z z+x =2 z x y z+x x+y y+z y z x 这个怎么证? fangchengzu:X+Z=Y 7Z=X+Y+Z X+Y+Z=14 x+y+z=12 x-y+z=2 x-z+y+a=90 x+y+a+z=100,求x y z a x=y; y=z; z=x/y 三元一次方程：x+y+z=26,x-y-z=-6,x+y-z=12 三元一次方程：x+y+z=26,x-y-z=-6,x+y-z=12 三元一次方程：x+y+z=26,x-y-z=-6,x+y-z=12