1- 10:BBACABBDBC
1 1:257
12:M=N
13: 13
14: positive and negative radical sign [2]
15:-45
16:2
17:25
18:2008
19:-20
20:5
2 1:7,8
22: 12,6
23:0.25ab, radical sign [0.5 (A 2+B 2)
24: 1,(x-y)(x^2-y^2+4xy)
25:40 degrees, 120 degrees