Question

P=4/1*5+4/5*9+4/9*13+...+4/21*25

Answer 1

rải chi tiết ra giúp mình với

 

Answer 2

bạn nào đúng minh tick

Answer 3

`P=4/1.5+4/5.9+4/9.13+...+4/21.25`

`=1-1/5+1/5-1/9+1/9-1/13+...+1/21-1/25`

`=1-1/25`

`=24/25`

Answer 4

Có: \(P=\dfrac{4}{1\times5}+\dfrac{4}{5\times9}+...+\dfrac{4}{21\times25}\)

\(P=1-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{9}+...+\dfrac{1}{21}-\dfrac{1}{25}\)

\(P=1-\dfrac{1}{25}=\dfrac{24}{25}\)

Answer 5

rải chi tiết ra mà bạn

Answer 6

\(P=\dfrac{4}{1\times5}+\dfrac{4}{5\times9}+\dfrac{4}{9\times13}+...+\dfrac{4}{21\times25}\)

\(=4\times\left(\dfrac{1}{1}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{13}+...+\dfrac{1}{21}-\dfrac{1}{25}\right)\)

\(=4\times\left(\dfrac{1}{1}-\dfrac{1}{25}\right)=4\times\left(\dfrac{25}{25}-\dfrac{1}{25}\right)\)

\(=4\times\dfrac{24}{25}=\dfrac{96}{25}.\)

Answer 7

\(P=\dfrac{4}{1\times5}+\dfrac{4}{5\times9}+\dfrac{4}{9\times13}+...+\dfrac{4}{21\times25}\)

\(=\dfrac{5-1}{1\times5}+\dfrac{9-5}{5\times9}+\dfrac{13-9}{9\times13}+...+\dfrac{25-21}{21\times25}\)

\(=1-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{13}+...+\dfrac{1}{21}-\dfrac{1}{25}\)

\(=1-\dfrac{1}{25}\)

\(=\dfrac{25}{25}-\dfrac{1}{25}\)

\(=\dfrac{24}{25}\)