Question

[Trần Nguyễn Mai Phương]

2/1x4+2/4x7+...+2/97x100

Answer 1

[Dora]

`2/[1xx4]+2/[4xx7]+...+2/[97xx100]`

`=2/3xx(3/[1xx4]+3/[4xx7]+...+3/[97xx100])`

`=2/3xx(1-1/4+1/4-1/7+...+1/97-1/100)`

`=2/3xx(1-1/100)=2/3xx99/100=33/50`

Answer 2

[꧁ ༺ ςông_ςɧúα ༻ ꧂]

\(\dfrac{2}{1.4}+\dfrac{2}{4.7}+...+\dfrac{2}{97.100}\)

\(=\dfrac{2}{3}.\left(\dfrac{3}{1.4}+\dfrac{3}{4.7}+...+\dfrac{3}{97.100}\right)\)

\(=\dfrac{2}{3}.\dfrac{99}{100}\)

\(=\dfrac{33}{50}\)