m+2d=mq^2 ……2

1 formula *2-2 formula omits m m≠0.

Yes: (q- 1) 2 = 0 ∴ q= 1 and if q= 1, the elements in the b set are not mutually exclusive.

So m+d = MQ 2.

m+2d=mq

Similarly, omitting d also has 2 * q 2-q- 1 = 0.

Q≠ 1, so q=- 1/2.