Question

2005+2*(1+2+3+......2004) este pătrat perfect.......cine il explica???

Answer 1

1+2+3+......+2004=2004*2005:2asta reiese din formula lui Gauss 1+2+3+...+n=n*(n+1):2


2005+2*(1+2+3+......+2004)=2005+2*2004*2005:2=2005+2004*2005=2005*(1+2004)=2005*2005=2005²  deci este patrat perfect

Answer 2

[tex]2005+2*(1+2+3+...+2004)=\\ 2005+\not2*\frac{2004*2005}{\not2}=\\ 2005+2004*2005=\\ 2005(1+2004)=2005^2[/tex]