Question

已知关于x ,y的方程组x-y=a+3与2x+y=5a的解满足x>0,y

Answer 1

x-y=a+3-----------------(1)

2x+y=5a-----------(2)

(1)+(2),3x=6a+3

x=(6a+3)/3

(1)*2,2x-2y=2a+6-----------(3)

(3)-(2),-3y=-3a+6,

y=(-3a+6)/-3

x〉0,y〈0

(6a+3)/3>0

(-3a+6)/-3