Question

如果直线x+（a-1）y+1=0与直线ax+2y+2=0互相平行，则a的值为______．

Answer 1

∵直线x+（a-1）y+1=0与直线ax+2y+2=0互相平行，∴

a

1

 =

2

a-1

≠

2

1

，即得a=-1，
故答案为-1．