Question

Tính:

\(E=\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}+\dfrac{1}{56}\)

Answer 1

 

E =16+112+120+130+142+156

 

E=\(\dfrac{1}{2.3}+\dfrac{1}{3.4}+\dfrac{1}{4.5}+\dfrac{1}{5.6}+\dfrac{1}{6.7}+\dfrac{1}{7.8}\)

 

 E=\(\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{1}-...+\dfrac{1}{7}-\dfrac{1}{8}\)

 

 E=\(\dfrac{1}{2}-\dfrac{1}{8}=\dfrac{3}{8}\)

Answer 2

E= \(\dfrac{3}{8}\)

Answer 3

Answer 4

E= \(\dfrac{1}{2.3}\) +\(\dfrac{1}{3.4}\) +\(\dfrac{1}{4.5}\) +\(\dfrac{1}{5.6}\) +\(\dfrac{1}{6.7}\) +\(\dfrac{1}{7.8}\)

E=\(\dfrac{1}{2}\) -\(\dfrac{1}{3}\) +\(\dfrac{1}{3}\) - \(\dfrac{1}{4}\) +...+\(\dfrac{1}{6}\) - \(\dfrac{1}{7}\) + \(\dfrac{1}{7}\) - \(\dfrac{1}{8}\)

E=\(\dfrac{1}{2}\) - \(\dfrac{1}{8}\)

E=\(\dfrac{3}{8}\) .

Đây là bài làm mà thầy tớ dạy trên trường nhé !

Answer 5

Ta có: \(E=\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}+\dfrac{1}{56}\)

\(=\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+\dfrac{1}{4\cdot5}+\dfrac{1}{5\cdot6}+\dfrac{1}{6\cdot7}+\dfrac{1}{7\cdot8}\)

\(=\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{8}\)

\(=\dfrac{1}{2}-\dfrac{1}{8}=\dfrac{3}{8}\)

Answer 6

\(E\text{=16+112+120+130+142+156}\)

\(E=\dfrac{1}{2.3}+\dfrac{1}{3.4}+\dfrac{1}{4.5}+\dfrac{1}{5.6}+\dfrac{1}{6.7}+\dfrac{1}{7.8}\)

\(E=\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-...+\dfrac{1}{7}-\dfrac{1}{8}\)

\(E=\dfrac{1}{2}-\dfrac{1}{8}=\dfrac{3}{8}\)