急!用加减消元法做!要有详细过程! x+3y+z=-1,2x-y+3z=7,3x+y+2z=3

x+3y+z=-1,--------->2x+6y+2z=-2 ①-2x-y+3z=7----,②-------->6x-3y+9z=21----(4)3x+y+2z=3----,③ -------> 6x+2y+4z=6 ----(5) ,② -①:-7y+z=9-------- -35y+5z=45---------(6)(4)-(5) -5y+5z=15 ------35y+35z...箭头什么意思?看题方便