2.= & lt

three

4-√3-2

5 1

6 x(x-y)(x+y) 2y(2x+ 1)^2

7 plus or minus 2 -4

8 x is greater than or equal to 3 and not equal to 4.

9/2 13

10 2 (√3+ 1)

1 1 3 1

12C

13D

14C

15 1

16 a cannot take 2. -2。 - 1，a+2= 1+2=3(a= 1)

17 y is not equal to 0 and x >；; =-25x & gt； 2

18 2a times the root number a.

19 A

20 arbitrary value

2 1 3-9 of root number 2

22( 1)20 9x-4 (2)x=5