(1+1+1+....+1).21
(21 số 1)
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
Tính nhẩm:
65 - 5 = 65 - 60 = 65 - 65 =
70 - 30 = 94 - 3 = 33 - 30 =
21 - 1 = 21 - 20 = 32 - 10 =
1+1+1+1+1+1+21=??
21=1 + ..............
1+1+2+3+5+8+...+21=?
1+1+1+1+1+1+1+1+1+1+1+1+21+1=
100+1+21
1+21