1.
x+2y=0 x=-2y
代入3x+2ay=18,整理,得
(a-3)y=9
y=9/(a-3)a≠3
要y为整数,则a只能为12,6,4,2,0,-6,满足题意的a共有6个.
2.
3x+2y=k+1(1)
4x+3y=k-1 (2)
(1)×3-(2)×2
x=k+5
(2)×3-(1)×4
y=-k-7
x>y k+5>-k-7k>-6
x-y>6
k+5+k+7>6k>-3
综上,得k>-3