已知满足2x-3y=11-4m和3x+2y=21-5m的x、y也满足x+3y=20-7m,则m的值为 _ .
问题描述:
已知满足2x-3y=11-4m和3x+2y=21-5m的x、y也满足x+3y=20-7m,则m的值为 ___ .
答
2x-3y=11-4m①,3x+2y=21-5m②,x+3y=20-7m③,
①+③得:x=
,31-11m 3
把它代入②得:y=-5+3m,
把x、y的值代入③得m=2.
故答案为:2.