联立两方程
4x-3y-6m=0.(1)
x+2y-7m=0.(2)
4(2)-(1)得 11y=22m y=2m
代入(2)式得 x=3m
再将x,y的值代入x+y+m/x-y+m 得 (3m+2m+m)/(3m-2m+m)=3