Cho \({\rm{M}} = \frac{{2013}}{1} + \frac{{2012}}{2} + \frac{{2011}}{3} + \ldots + \frac{1}{{2013}};{\rm{N}} = \frac{1}{2} + \frac{1}{3} + \frac{1}{4} + \ldots + \frac{1}{{2014}}\). Khi đó
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Lời giải:
Báo sai\(\begin{array}{l} {\rm{M}} = \frac{{2013}}{1} + \frac{{2012}}{2} + \frac{{2011}}{3} + \ldots + \frac{1}{{2013}}\\ = \left( {\frac{{2013}}{1} + 1} \right) + \left( {\frac{{2012}}{2} + 1} \right) + \left( {\frac{{2011}}{3} + 1} \right) + \ldots + \left( {\frac{1}{{2013}} + 1} \right) - 2013\\ = 2014 + \frac{{2014}}{2} + \frac{{2014}}{3} + \ldots + \frac{{2014}}{{2013}} - 2013\\ = 2014\left( {\frac{1}{2} + \frac{1}{3} + \frac{1}{4} + \ldots + \frac{1}{{2013}}} \right) + 1\\ = 2014\left( {\frac{1}{2} + \frac{1}{3} + \frac{1}{4} + \ldots + \frac{1}{{2013}}} \right) + \frac{{2014}}{{2014}}\\ = 2014\left( {\frac{1}{2} + \frac{1}{3} + \ldots + \frac{1}{{2013}} + \frac{1}{{2014}}} \right) = 2014.{\rm{N}}\\ \Rightarrow {\rm{M}} = 2014.{\rm{N}} \end{array}\)