Question

Tính \(\dfrac{P}{A}\)biết :

P=\(\dfrac{2013}{2}+\dfrac{2013}{3}+\dfrac{2013}{4}+...+\dfrac{2013}{2014}\)

A = \(\dfrac{2013}{1}+\dfrac{2012}{2}+\dfrac{2011}{1}+....+\dfrac{1}{2013}\)

Answer 1

\(A=\dfrac{2013}{1}+\dfrac{2012}{2}+\dfrac{2011}{3}+...+\dfrac{1}{2013}\)

\(=\left(\dfrac{2012}{2}+1\right)+\left(\dfrac{2011}{3}+1\right)+...+\left(\dfrac{1}{2013}+1\right)+1\)

\(=\dfrac{2014}{2}+\dfrac{2014}{3}+...+\dfrac{2014}{2013}+\dfrac{2014}{2014}\)

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

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

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

Vậy \(\dfrac{P}{A}=\dfrac{2013}{2014}\)