解三元一次方程.快.3X+y-4z=13,5x-y+3z=5,x+y-z=3

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解三元一次方程.快.3X+y-4z=13,5x-y+3z=5,x+y-z=3
解三元一次方程.快.
3X+y-4z=13,5x-y+3z=5,x+y-z=3

解三元一次方程.快.3X+y-4z=13,5x-y+3z=5,x+y-z=3
3X+y-4z=13,①
5x-y+3z=5②
,x+y-z=3③
①+②得
8x-z=18④
②+③得
3x+z=4⑤
④+⑤得
11x=22
x=2
代入⑤ z=-2
代入③ y=-1

3X+y-4z=13 ①
5x-y+3z=5 ②
x+y-z=3 ③
①+ ②得8x-z=18 ④
②+③得6x+2z=8 ⑤
④*2+⑤得22x=44 所以x=2
将X=2带入④得 z=-2
将x=2,z=-2带入③得y=-1
所以:x=2,y=-1,z=-2