Question

cum se calculeaza 1^{2} +3^{2} +5^{2} +----------+2009^{2}

Answer 1

1^2 +3^2 +5^2 +----------+n^2=n(n+1)(2n+1)/6

1^2 +3^2 +5^2 +----------+2009^2 =2009·2010·4019/6

=2009·335·4019

Answer 2

Se folosește rezultatul :

$\it 1^2+3^2+5^2+ ...+(2n-1)^2 = n\cdot\dfrac{4n^2-1}{3}$