TimA;Biết A=300+298+296+...+202-297-296-...-201
tính bằng cách hợp lý:
a) (1981.1982-990):(1980.1982+992)
b) 302+301-300-299+298+297-296-295+...+6+5-4-3+2+1
A = 1+2+3-4-5-6+7+8+9-10-11-12+.....+ 295+ 296 + 297 - 298 - 299 - 300 + 301
tinh A
a, A= 2100 - 299 - 298 - 297 - ... - 2 -
A=2100-299+298-297+...-23+22-2+1
HELP ME
CMR :
2100 - 299 + 298 - 297 + ...... + 24 - 23 + 22 ⋮ 12
a, A = 1 + 2 + 22 + 23 + ... + 250 =
b, B = 1 + 3 + 32 + 33 + ... 3100 =
c, C = 5 + 52 + 53 + ... 530 =
d, D = 2100 = 299 + 298 - 297 + ... + 22 - 2
C=1-2-3+4+5-6-7+8-...-297-298-299+300+301
tính:
1+2-3-4+5+6-7-8+...+297+298-299-300