101-102-(-103)-104-(-105)-106-(-107)-108-(-109)-110
tính tổng đại số sau
a)2-4+6-8+...+1998-2000
b)11-12+13-14+15-16+17-18+19-20
c)101-102-(-103)-104-(-105)-106-(-107)-108-(-109)-110
101 - 102 + 103 - 104 + 105 - 106 +........+ 997 - 998 + 999 = ?
tinh nhanh: 101 - 102 + 103 - 104 + 105 - 106 +........ + 997 - 998 + 999
Chứng minh rằng: 1/5+1/20+1/21+1/22+1/23+1/24+1/25+1/101+1/102+1/103+1/104 +1/105<1/2
Chứng minh rằng: 1/5+1/20+1/21+1/22+1/23+1/24+1/25+1/101+1/102+1/103+1/104 +1/105<1/2
1 + 2 + 3 + 4 ..... 99 + 100 + 101 + 102 +103 + 104 ..... 189 + 199 = ?
100+101+102+103+104+.......................+199+200=?????
cac ban giup minh nha!