So A=B

So x? +(m+ 1)x+m=x？ +3x+2

Get m=2.

2. Replace b with {2,3} and c = {-4,2}.

Because A∩B ≠ empty set, A∩C= empty set.

So 2 doesn't belong to a, and 3 belongs to a.

Substitute x=3 into x? -ax+a？ - 19=0 (x+2)(x-5)=0。

Get a=-2 or a=5.

When a=-2, A={x|x? +2x- 15}={3，-5}

When a=5, A={x|x? -5x+6} = {2,3}, and an ∩C≠ empty set is discarded at this time.

To sum up, a=-2

I hope I can help you ~