Question

a thôi nhé

 

Answer 1

`A=3/(2xx5) + 3/(5xx8) + 8/(8xx11) + 3/(11xx14)`

`A=(5-2)/(2xx5)+(8-5)/(5xx8)+(11-8)/(8xx11)+(14-11)/(11xx14)`

`A=5/(2xx5)-2/(2xx5)+8/(5xx8)-5/(5xx8)+11/(8xx11)-8/(8xx11)+14/(11xx14)-11/(11xx14)`

`A=1/2-1/5+1/5-1/8+1/8-1/11+1/11-1/14`

`A=1/2-1/14`

`A=3/7`

 

 

Answer 2

\(A=\dfrac{3}{2\times5}+\dfrac{3}{5\times8}+\dfrac{3}{8\times11}+\dfrac{3}{11\times14}\)

\(A=\dfrac{1}{2}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{11}+\dfrac{1}{11}-\dfrac{1}{14}\)

\(A=\dfrac{1}{2}-\dfrac{1}{14}\)

\(A=\dfrac{7}{14}-\dfrac{1}{14}\)

\(A=\dfrac{6}{14}=\dfrac{3}{7}\)