CHO N LÀ SỐ NGUYÊN DƯƠNG THỎA MÃN 2(C C C22+ 32+ 42+...CN2)=3AN2+1. S...
(
C C C2
2
+3
2
+4
2
+...Cn
2
)
=3An
2
+
1
. Sau khi khai triển và rútn
n
gọn thì biểu thức − 12
2
+3
−1x xx x có tất cả bao nhiêu số hạng. A. 30. B. 28 . C. 29 . D. 32.---
STT
110
138
210
232
354
392
476
598
610
792
874
956
1
A
B
A
D
C
B
B
C
D
B
B
A
2
A
C
A
D
B
A
C
D
A
A
D
D
3
C
A
D
A
D
A
D
A
D
C
C
A
4
A
C
B
C
D
C
B
C
B
C
D
D
5
D
D
C
D
C
C
C
C
B
C
C
B
6
D
A
D
B
A
A
D
C
D
C
A
B
7
C
B
A
C
B
A
C
D
B
A
D
A
8
B
B
A
A
B
A
B
A
B
B
C
C
9
C
A
D
D
D
B
D
B
C
B
B
D
10
D
A
B
B
B
A
B
A
C
D
C
B
11
B
B
C
C
A
D
A
C
D
A
A
B
12
D
A
A
A
B
A
A
B
A
A
B
A
13
D
A
D
B
A
B
D
D
D
A
A
A
14
A
B
C
D
A
B
A
C
B
B
A
C
15
A
D
B
D
A
B
D
A
A
A
B
D
16
B
D
B
C
B
A
B
D
A
C
D
C
17
D
D
A
A
B
D
C
A
C
C
B
D
18
B
C
B
C
D
D
C
A
D
C
D
B
19
D
A
B
B
C
C
A
D
C
D
D
C
20
A
B
D
D
C
B
A
B
B
B
B
D
21
D
D
C
A
C
A
C
A
B
B
A
B
22
A
A
B
B
A
D
D
D
C
D
D
A
23
B
D
A
D
D
C
C
C
D
B
B
A
24
D
C
C
D
C
C
D
C
D
B
D
D
25
B
B
C
A
A
D
B
D
C
D
D
C
26
C
C
C
D
D
B
C
D
D
D
C
D
27
B
A
B
D
D
C
D
B
C
C
C
D
28
D
B
B
A
A
B
A
B
C
D
A
D
29
A
C
B
C
A
D
A
B
A
B
C
C
30
C
A
D
A
A
A
A
A
B
D
B
A
31
C
C
D
C
B
C
B
A
C
B
A
A
32
D
D
D
A
C
C
D
D
B
D
A
C
33
A
C
C
D
D
C
A
B
A
A
C
B
34
D
B
C
C
B
A
D
C
C
C
B
A
35
D
D
A
B
A
D
C
A
A
A
A
C
36
C
B
B
C
D
D
B
A
B
D
B
C
37
C
C
B
D
B
C
A
C
A
B
C
A
38
A
D
A
B
D
B
A
B
A
B
A
C
39
A
C
B
C
B
B
C
A
D
A
C
B
40
B
A
A
B
C
C
B
D
D
C
B
B
41
C
A
A
B
C
B
D
B
D
C
B
B
42
B
C
D
D
C
D
B
C
C
A
B
D
43
D
C
C
C
B
D
C
B
C
B
C
C
44
B
D
D
A
D
B
C
B
B
B
B
A
45
B
D
A
B
C
A
D
C
B
A
D
A
46
B
B
B
C
B
C
B
D
C
D
A
B
47
C
B
D
B
C
D
C
A
A
D
C
D
48
A
C
D
B
D
C
C
A
A
A
D
B
49
C
D
C
A
B
D
A
B
A
C
A
C
50
C
C
C
A
A
C
B
D
A
D
D
A