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

Răspuns :

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





Se folosește rezultatul :


[tex]\it 1^2+3^2+5^2+ ...+(2n-1)^2 = n\cdot\dfrac{4n^2-1}{3}[/tex]