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a)n=2015+2ori(1+2+3+..+2014)

b)aratati ca n e patrat perfect



Răspuns :

În paranteză ai suma lui Gauss
[tex] \frac{2014(2014+1)}{2} [/tex]
[tex]2015+2* \frac{2014*2015}{2} = \\ 2015+2014*2015= \\ 2015(1+2014)= \\ 2015^2[/tex]
=>n=pătrat perfect
[tex]n=2015+2*(1+2+3+...+2014) \\\\ n=2015+2 *\frac{(1+2014)*2014}{2} \\\\ n=2015+(1+2014)*2014 \\\\ n= 2015+2015*2014 \\\\ n=2015(1+2014) \\\\ n=2015*2015 \\\\ \boxed{n=2015^2\to este \ p.p}[/tex]