Toán Helpppp S = 1.2 + 2.3 + 3.4 +…..+ 99.100 05/07/2021 By Ariana Helpppp S = 1.2 + 2.3 + 3.4 +…..+ 99.100
Đáp án: `S = 1 . 2 + 2 . 3 + 3 . 4 + ……………… + 99 . 100` `3S = 1 . 2 . 3 + 2 . 3 . 3 + 3 . 4 . 3 + ………. + 99 . 100 . 3` `3S = 1 . 2 . 3 + 2 . 3 . ( 4 – 1) + 3 . 4 . ( 5 – 2) + ………. + 99 . 100 . (101 – 98)` ` = 1 . 2 . 3 – 1 . 2 . 3 + 2 . 3 . 4 – 2 . 3 . 4 + ……… – 98 . 99 . 100 + 99 . 100 . 101` ` = 99 . 100 . 101` ` S =(99 . 100 . 101)/3` ` = 33 . 100 . 101 = 3300 . 101 = 333300` `text{ Mathvietnam2k8}` Trả lời
Đáp án + Giải thích các bước giải: `S=1.2+2.3+3.4+…+99.100` `=>3S=1.2.3+2.3.3+3.4.3+…+99.100.3` `=>3S=1.2.(3-0)+2.3.(4-1)+3.4.(5-2)+…+100.99.(100-98)` `=>3S=(1.2.3+2.3.4+3.4.5+…+99.100.101)-(0.1.2+1.2.3+2.3.4+…+98.99.100)` `=>3S=99.100.101-0.1.2` `=>3S=99.100.101-0` `=>3S=99.100.101` `=>3S=999900` `=>S=333300` Trả lời
Đáp án:
`S = 1 . 2 + 2 . 3 + 3 . 4 + ……………… + 99 . 100`
`3S = 1 . 2 . 3 + 2 . 3 . 3 + 3 . 4 . 3 + ………. + 99 . 100 . 3`
`3S = 1 . 2 . 3 + 2 . 3 . ( 4 – 1) + 3 . 4 . ( 5 – 2) + ………. + 99 . 100 . (101 – 98)`
` = 1 . 2 . 3 – 1 . 2 . 3 + 2 . 3 . 4 – 2 . 3 . 4 + ……… – 98 . 99 . 100 + 99 . 100 . 101`
` = 99 . 100 . 101`
` S =(99 . 100 . 101)/3`
` = 33 . 100 . 101 = 3300 . 101 = 333300`
`text{ Mathvietnam2k8}`
Đáp án + Giải thích các bước giải:
`S=1.2+2.3+3.4+…+99.100`
`=>3S=1.2.3+2.3.3+3.4.3+…+99.100.3`
`=>3S=1.2.(3-0)+2.3.(4-1)+3.4.(5-2)+…+100.99.(100-98)`
`=>3S=(1.2.3+2.3.4+3.4.5+…+99.100.101)-(0.1.2+1.2.3+2.3.4+…+98.99.100)`
`=>3S=99.100.101-0.1.2`
`=>3S=99.100.101-0`
`=>3S=99.100.101`
`=>3S=999900`
`=>S=333300`