S=1+2+3+…+2007
S=21+23+25+…+1001
S=2+4+6+…+998+1000
S=1+2+2^2+2^3+…+2^200
S=1+2+3+…+2007 S=21+23+25+…+1001 S=2+4+6+…+998+1000 S=1+2+2^2+2^3+…+2^200
By Jasmine
By Jasmine
S=1+2+3+…+2007
S=21+23+25+…+1001
S=2+4+6+…+998+1000
S=1+2+2^2+2^3+…+2^200
1) S = 1+2+3+…+2007
Số số hạng : (2007 -1 ) : 1 +1 = 2007
Tổng dãy : ( 1 + 2007 ) . 2007 : 2 = 2015028
2) S = 21+23+25+…+1001
Ssh : ( 1001 – 21 ) : 2 + 1 = 491
Tổng dãy : ( 1001 + 21 ) . 491 : 2 = 250901
3) S=2+4+6+…+998+1000
Ssh : ( 1000 – 2 ) : 2 + 1 = 500
Tổng dãy : ( 1000 + 2 ) . 500 : 2 = 250500
`1) S = 1+2+3+…+2007`
`Tổng dãy : ( 1 + 2007 ) .[(2007 -1 ) : 1 +1]: 2 = 2015028`
`2) S = 21+23+25+…+1001`
`Tổng dãy : ( 1001 + 21 ) .[ ( 1001 – 21 ) : 2 + 1 = 491] : 2 = 250901`
`3) S=2+4+6+…+998+1000`
`Tổng dãy : ( 1000 + 2 ) .[( 1000 – 2 ) : 2 + 1 = 500] : 2 = 250500`