Question

已知2x+5y-9=0,mx+2y=8,5x-6y=4三个方程有公共解,求m的值

Answer 1

2x+5y-9=0 (1)

5x-6y=4 (2)

(1)×6+(2)×5

12x+30y-54+25x-30y=20

37x=74

x=2

y=(9-2x)/5=1

代入mx+2y=8

2m+2=8

m=3