2+6+12+20+30+42=42+20+12+6+2+?
1+1+1+1+1+1+1+11+1+121+12+12+12+1+2+42+42+25+35=?
1-24*12912+4242+24+2*4-412+2+42-121+24+5-12*12+1+*2*1-2+42+4-4-4*-55+-21-24*4-1+2-2*4-2+12+12*4*-212+124-4-2+1+2-421+12*4-21+0124*2-4+2+12422-4+2124-2-4+412*1221+1212+21+21
100+22+38+42
2=6
3=12
4=20
5=30
6=42
9=???????????
40 x 41 + 41 x 42 + .... + 99 x 100
90:9=
12:12=
63:6=
42:7=
Viết số liền trước của mỗi số sau:
35 ; 42; 70; 100; 1.
..............................
Nếu:
2 = 6
3 = 12
4 = 20
5 = 30
6 = 42
9 = ??