Question

关于xy方程组{x+2y=5m,x-y=-4的解是方程2x+3y=6的一组解，则m=——

Answer 1

22/25解：解方程组x-y=-4 2x+3y=6可得x=-6/5 y=14/5 代入x+2y=5m可得m=22/25

Answer 2

x + 2y = 5mx -y = -4 ==> 3y = 5m + 4==> y = (5m +4) /3 x = y - 4 = (5m +4) /3 - 4 = (5m - 8) /3 2x+3y= 6==> 2 * (5m -8) / 3 + 3 * (5m +4)/ 3 = 6==> 2 * (5m -8) + 3(5m + 4) = 18==> 10m - 16+ 15m + 12 = 18==> 25m = 22==> m = 22/25

Answer 3

先由前两个式子求的x=-m，y=3m
然后将求得的x，y的值带入到2x+3y=6
解得m=6/7