1，-2i

2, greater than or equal to-1

3, 1/2

4, 1

5,( 1,2]

6, 32 or 64 Parties

7, 2/5

8, 4/7

9,8 or 1 or 1/8

10，x-4y+3=0

1 1,3/4

12,2 root number 2

C A B D

17, (1) The root number of the reduction to absurdity (2)2/3

18, when A 2 and B 5, the maximum is 20.

19,( 1) 4 (2)

20, (1) y 2 = 4x (2) divided by (4,0)

2 1, (1) equidistant p=2 q= 1 equidistant p=-r q=0.

(2), (3) I don't have the answer here, but the way of (2) is that after the formula is listed, both sides are divided by 2 n to form a arithmetic progression.