二元一次方程组 ①x+y/2+x-y/3=7 ②x+y/3-x-y/4=-1换元法解

x+y/2+x-y/3=7 ①x+y/3-x-y/4=-1 ②设x+y=m x-y=n则方程组变为 m/2+n/3=7 3m+2n=42 (1)m/3-n/4=-1 4m-3n=-12 (2)(1)*3+(2)*2 17m=102 m=6代入(1) n=12于是x+y=6 (3)x-y=12 (4)(3)+(4) 2x=18 x=9代入(3) y=-3...