Formulă:
[tex]1+3+5+7+...+n = \Big(\dfrac{n+1}{2}\Big)^2[/tex]
Rezovare:
[tex]\dfrac{1}{10}+\dfrac{3}{10}+\dfrac{5}{10}+...+\dfrac{19}{10} = \dfrac{1}{10}\cdot(1+3+5+...+19) = \\ \\ = \dfrac{1}{10}\cdot \Big(\dfrac{19+1}{2}\Big)^2 = \dfrac{1}{10}\cdot \Big(\dfrac{20}{2}\Big)^2 = \dfrac{1}{10}\cdot 10^2 = 10[/tex]
