Question

Aratati ca numarul N=1+3+5+...+3999 este patrat perfect

Answer 1

Folosim formula:   $1+3+5+...+n = (\frac{n+1}{2})^{2}$
Si avem:

$N =1+3+5+...+3999= (\frac{3999+1}{2})^{2} = (\frac{4000}{2})^{2} = 2000^{2}$

=> N este patrat perfect