满足2x-3y=11-4m和3x+2y=21+5m的x,y,也满足x+3y=10+7m求m

题目

满足2x-3y=11-4m和3x+2y=21+5m的x,y,也满足x+3y=10+7m求m

答案

2x-3y=11-4m①
3x+2y=21+5m②
x+3y=10+7m③
①+③,得3x=21+3m,x=7+m
①*2+②*3,得13x=22-8m+63+15m,13x=85+7m
13(7+m)=85+7m
91+13m=85+7m
5m=-6
m=-6/5