1+2-3-4+5+6-7-8 +.............+297+298-299-300
= (1+2)-(3+4)+(5+6-(7+8)+.........+(297+298)-(299+300)
=3-7+11-15+.......+595-599
= (3+11+......+595)-(7+15+...........+599)
=22425-22725
= (-300)
C=1-2-3+4+5-6-7+8-...-297-298-299+300+301
Tính hợp lí
1 + 2 - 3 - 4 + 5 + 6 - 7 - 8 + ... + 297 + 298 - 299 - 300 +301
Help
:'(
A = 1+2+3-4-5-6+7+8+9-10-11-12+.....+ 295+ 296 + 297 - 298 - 299 - 300 + 301
tinh A
tinh nhanh 1-2-3+4+5-6-7+...+297-298-299+300+301-302-303+304+305
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
thực hiện phép tính 1 cách hợp lí
a, 1+3+5+... +79
b, 3+6+9+...+2007
c,100+98+98+...+2-99-97-...-1
d, 99-97+95-93+...+3-1
e, 1-2+3-4+...+1997-1998+1999
g, 5+6-7-8+9+10-...+297+298-299-300+301+302
tính tổng A
A= 1+2-3-4+5+6-7-8+9+10-11-12+.........+298-299-300+301
1+2-3-4+5+6-7-8+....+298-299-300+301+302
1+2-3-4+5+6-7-8+9+10-11-12+........+298-299-300+301+302 = ?
