2, 5/2

3, (-4,-3)

Four, two, four

5,60 degree radical sign 3/3

6. x < = 5 and x is not =-2.

7, -7 -5/3

8, (3,6) (- 1,-2)

9, Y=-2(X-2) squared+2 (2,2)

10，K & gt- 1/3

1 1，A 12，C 13，A 14，A 15，D 16，C 17，B 18，D

19, (x-3)/(x+1)+(x+1)/(x-3) = 5/2 (x is not equal to 3 and-1).

[(X-3) square +(X+ 1) square ]/[(X+ 1)(X-3)]=5/2.

(X-6X+9+X+2X+ 1)/(X-2X-3)= 5/2。

2(2X square -4X+ 10)=5(X square -2X-3)

4X Square -8X+20=5X Square-10X- 15

X squared -2X-35=0

(X-7)(X+5)=0

X=7 or -5