Question

Demonstrati ca numarul : 2006 + 2 (1+2+3+...+2005) este patrat perfect.

Answer 1

 2006 + 2×(1+2+3+...+2005)=
=2006+2×2005×2006/2=
=2006+2005×2006=
=2006×(1+2005)=
=2006×2006=
=2006²

Answer 2

=2006+2×2005×2006/2
=2006+2005×2006
=2006(1+2005)
=2006×2006
=2006²