4x-9z=17 3x+y+15z=18 x+2y+3z=2①-②×③,得：4X-6Z=9 ④④×⑤-③×6,得X=-3/4把X=-3/4代入①,得：Y=5/3把X=-3/4,代入④,得：Z=2所以……………………解为{X=-3/4{Y=5/3{Z=22x+4y+3z=93x-2y+5z=11 x-6y+7z=13 ②×...