Question

当m为何值时方程3mx+2-m=0的解为x= 负2

Answer 1

3x-y=2k-1 (1)

4x+2y=k (2)

(1)*2+(2)

10x=4k-2+k=5k-2

x=(5k-2)/10

由(1),y=3x-2k+1=3(5k-2)/10-2k+1

x>0,(5k-2)/10>0,5k-2>0,k>2/5

y>0,3(5k-2)/10-2k+1>0.3(5k-2)/10>2k-1,15k-6>20k-10,5k