Giúp mình với ạ
\(=\dfrac{1}{2014}-\dfrac{1}{2014}+\dfrac{1}{2013}-\dfrac{1}{2013}+\dfrac{1}{2012}-...-\dfrac{1}{3}+\dfrac{1}{2}-\dfrac{1}{2}+1=1\)
\(\dfrac{1}{2014}-\dfrac{1}{2014.2013}-\dfrac{1}{2013.2012}-...-\dfrac{1}{3.2}-\dfrac{1}{2.1}\)
\(=\dfrac{1}{2014}-\left(\dfrac{1}{2014}-\dfrac{1}{2013}\right)-\left(\dfrac{1}{2013}-\dfrac{1}{2012}\right)-...-\left(\dfrac{1}{3}-\dfrac{1}{2}\right)-\left(\dfrac{1}{2}-\dfrac{1}{1}\right)\) \(=\dfrac{1}{2014}-\dfrac{1}{2014}+\dfrac{1}{2013}-\dfrac{1}{2013}+\dfrac{1}{2012}-\dfrac{1}{2012}+...+\dfrac{1}{3}-\dfrac{1}{3}+\dfrac{1}{2}-\dfrac{1}{2}+1\) \(=1\)
