当m取何值时,方程组{x-2y=1-2分之m,3x+4y=2m}的解满足不等式x-y
问题描述:
当m取何值时,方程组{x-2y=1-2分之m,3x+4y=2m}的解满足不等式x-y
答
x-2y=1-m/2.(1)
3x+4y=2m.(2)
(1)*2+(2)得:5x=2+m.(3)
(2)-(1)*3得:10y=7m/2-3.(4)
(3)*2-(4)得:10(x-y) = 7-3m/2
x-y=(14-3m)/20
x-y<0
∴14-3m<0
∴m>14/3