Question

详细点写~~!（过程详细哈!）1、在关于x、y的方程组｛2x+y=1-m,3x+4y=2｝中,若x、y满足x+y>3,求

Answer 1

1）解方程组：8x+4y=4-4m (减2)=> 5x=2-4m => x=(2-4m)/5 (代入1）=> y=1-m-2(2-4m)/5 => y=(3m-1)/5

∴ （2-4m)/5+(3m-1)/5>3 => 2-4m+3m-1>15 => -m> 14

∴m4(11-8-20/60)

2v/3>32/3 =>2v>32 =>v>16 (km/h) 答：至少应是每小时16千米.