解方程组
x-2y-z=1,……………………………………………………①
x+4y+3z=1,…………………………………………………②
x+4y+z=5……………………………………………………③
②-③,得2z=-4
即,z=-2
把z=-2代回①、②,得
x-2y=-1
x+4y=7
解得,x=5/3,y=4/3
∴原方程组的解为x=5/3,y=4/3,z=-2
x-2y-z=0,2x+y-z=1,3x+2y-z=4方程组的解z=2,2x+3y=6,4x-z=10x-y+2z=5,2x+y-z=1,3x-z=03x+2y+5z=2,x-2y-z=6,4x+2y-7z=30
【第一题】①x-2y-z=0,②2x+y-z=1,③3x+2y-z=4②-①,③-②,消去z,得x+3y=1,x+y=3解得,x=4,y=-1,z=6【第二题】z=2,2x+3y=6,4x-z=10把z=2代入4x-z=10,解得x=3,把x=3代入第二个方程,得y=0∴x=3,y=0,z=2【第三题】①x-y+2z=5,②2x+y-z=1,③3x-z=0由③得z=3x,代回另外两个方程,得7x-y=5,-x+y=1解得,x=1,y=2,则z=3【第四题】①3x+2y+5z=2,②x-2y-z=6,③4x+2y-7z=30①+②,②+③,消去y,得4x+4z=8,5x-8z=36解得,x=4,z=-2,则y=0