Question

Voi da coroana!
ex:5

Answer 1

$2015 + 2 \times 2014 \times 2015 \div 2 = 2015 \times (2015 + 1) = 2015 \times 2015 = {201}^{2}$
este egal cu

Answer 2

in paranteza e o suma Gauss pe care o calculezi cu formula S=n(n+1)/2

=> nr. va fi: 2015+2·(2014·2015)/2=2015+2014·2015=2015(1+2014)=2015², deci e patrat perfect