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2015+2×(1+2+3.....+2014)​

Răspuns :

 

[tex]\displaystyle\bf\\2015+2\times(1+2+3+...+2014)=\\\\=2015+2\left[\frac{2014(2014+1)}{2} \right]=\\\\=2015+2014(2014+1)=\\\\=2015+2014\times2015=\\\\=2015(1+2014)=2015\times2015=\boxed{\bf2015^2}[/tex]