Question

Answer 1

f: ta có: \(\dfrac{1}{2014}-\dfrac{1}{2014\cdot2013}-...-\dfrac{1}{3\cdot2}-\dfrac{1}{2\cdot1}\)

\(=\dfrac{1}{2014}-\left(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{2013}-\dfrac{1}{2014}\right)\)

\(=\dfrac{1}{2014}-\dfrac{2013}{2014}\)

\(=\dfrac{-2012}{2014}=\dfrac{-1006}{1007}\)

Answer 2

b. \(\dfrac{5}{3}+\left(-\dfrac{2}{7}\right)-\left(-1,2\right)\)

= \(\dfrac{35}{21}+\dfrac{-6}{21}+\dfrac{25,2}{21}\)

= \(\dfrac{35+\left(-6\right)+25,2}{21}\)

= \(\dfrac{54,2}{21}\)