`= 1/3 - 1/5 + 1/5 - 1/7 + 1/7 - 1/9 + 1/9 - 1/11 + 1/11 - 1/13 + 1/13 - 1/15 + 2/(1xx2) + ... + 2/(9xx10)`
`= 4/15 + 1/2 . 9/10`
`= 4/15 + 9/20`
`= 43/60`
2/3x5+2/5x7+2/7x9+2/9x11+.......+2/25x27.Tính nhanh.
2/1x2 + 2/2x3 + 2/3x4 + 2/4x5 + 2/5x6 + 2/6x7 + 2/7x8 + 2/8x9 + 2/9x10 ( Trả lời rõ ràng ạ
2/1x3+2/3x5+2/5x7+2/7x9+2/9x1+2/11x13
Tính tổng sau bằng cách hợp lí:
A = 2/1x3 + 2/3x5 + 2/5x7 + 2/7x9 + 2/9x11
\(\dfrac{2}{1x3} + \dfrac{2}{3x5} + \dfrac{2}{5x7} + \dfrac{2}{7x9} + \dfrac{2}{9x11}\)
\(\dfrac{2}{1x3}+\dfrac{2}{3x5}+\dfrac{2}{5x7}+\dfrac{2}{7x9}+\dfrac{2}{9x11}\)
giúp mik với ạk
\(\frac{2}{1x3}+\frac{2}{3x5}+\frac{2}{5x7}+........+\frac{1}{11x13}+\frac{1}{13x15}\)
ai đúng sẽ k cho người đó
Bài 1 tính nhanh a,1/3x4+1/4x5+1/5x6+.....+1/2018x2019+1/2019x2020 b,2/3x5+2/5x7+2/7x9+.....+2/99x101 c,1/2+1/6+1/12+1/20+1/30+1/42+1/56 huhuhu.....
( 1/3x5 + 1/5x7 + 1/7x 9 + 1/9x11 + 1/11x13 ) x X= 2/3
Tính : B = 2/1x3 + 2/3x5 + 2/5x7 + 2/7x9 + ..... + 2/99x101
