5x-3y+4z=13,2x+7y-3z=19,3x+2y-z=185x-3y+4z=13 (1)2x+7y-3z=19 (2) 3x+2y-z=18 (3)这题我是这样做的,把3x+2y-z=18 (3)写成-z=-3x-2y+18 变号写成 z=3x+2y-18可以不?z=3x+2y-18 （4）把（4）代入（1）得5x-3y+4(3x+2y-18)=13 5x-3y+12x+8y

三元一次方程解 1.{x+y-z=5 {3x+2y+z=2 {2x-2y+z=-31.{x+y-z=5 2.{9x-5y+x=-6 3.{x-y=3 4.{x+y=3 5.{4x-2y+z=7{3x+2y+z=2 {9x+y-2z=3 {x+z=7 {y+z=4 {2x-y-3z=28{2x-2y+z=-3 {-9x+3y-5z=0 {y-z=6 {z+x=5 {x+y-2z=13 ..1.x+y+z=26,2.4y+3z=7,y-z=1,3x+2z=17,x+2y-z=18 9x-7y=173.x-7y+3z=17 4.2x+4y+3z=95x-6y-z=24 3x-2y+5z=113x+7y-2z=1 5x-6y+7z=131.x+y+z=26,y-z=1x+2y-z=18 2.4y+3z=7,3x+2z=11,9x-7y=17 3.x-7y+3z=17 5x-6y-z=24 3x+7y-2z=14.2x+4y+3z=93x-2y+5z=11 5x-6y+7z=13 (1)2X+4Y+3Z=93X-2Y+5Z=115X-6Y+7Z=13(2)X:Y=3:2Y:Z=5:4X+Y+Z=66(3)3X-Y+Z=32X+Y-3Z=11X+Y+Z=13以上3个题目为三元一次方程~ 六年级三元一次方程组.解下列方程组：(1)5x-3y+z=25x+2y-4z=3-5x+y-z=2(2)x-y-z=-13x_5y+7z=114x-y+2z=-1(3)9x-5y+z=-69x+y+4z=3-9x+3y-5z=0(4)x+y=22x+z=-27y+z=13 1.5x-3y+z=25x+2y-4z=3-5y+y-z=2以上是第一题.2.x+y=-2x+z=13y+z=1以上是第二题.3.x-y-z=-13x+5y+7z=114x-y+2z=-1以上是第三题. 5x+2y=5,y-z=-7,4z+3x=13 5x+2y=5,y-z=-7,4z+3x=13 六年级三元一次方程组第一题：{5x-3y+z=2 5x+2y-4z=3 -5x+y-z=2第二题：{x+y=-2 x+z=13 y+z=1第三题：{x-y-z=-1 3x+5y+7z=11 4x-y+2z=-1 方程组3x+y-4z=1 2x-y-2z=6 5x+3y-3z= --1/2{负二分之一} x=?y=?z=?3x+2y+z=13 x+y+2z=7 2x+3y-z=12 x=?y=?z=? 解下列方程 三元一次方程一、 5x-3y+z=25x+2y-4z=3-5x+y-z=2二、x+y=-2x+z=13y+z=1三、x-y-z=-13x+5y+7z=114x-y+2z=-1第二题不用了 5x+4y+z=0 3x+y-4z=13 x+y+z=—2 -2X+3Y+Z=-4-X-5Y-2Z=-13X+Y-Z=10 2x+5y+4z=6,3x+y-7z=-4,x+y-z=? 已知2x+5y+4z=6 3x+y-7z=-4求x+y-z X-Y-Z=0 X+Y-3Z=4 2X-5Y+7Z=21 3x+7y+4z=35,x+5y+2z=40,x+y+z=( ) {x+y+z=1 {x+3y+7z=2 {x+5y+19z=4 5x+3y+2z=2011 4x+6y+7z=2012 求x+y+z