Question

[Võ Xuân Dũng]

1/2 + 1/6 +1/12 +1/20 + 1/30 +1/42+ 1/56

Answer 1

[hmmmm]

\(\dfrac{7}{8}\)

Answer 2

[OH-YEAH^^]

\(\dfrac{1}{2}+\dfrac{1}{6}+...+\dfrac{1}{56}\)

=\(\dfrac{1}{1.2}+\dfrac{1}{2.3}+...+\dfrac{1}{7.8}\)

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

=\(1-\dfrac{1}{8}=\dfrac{7}{8}\)