[tex] \it \dfrac{1}{2\cdot3} = \dfrac{1}{2}- \dfrac{1}{3}
\\ \\ \\
\dfrac{1}{3\cdot4} = \dfrac{1}{3} - \dfrac{1}{4}
\\ \\ \\
\dfrac{1}{4\cdot5} = \dfrac{1}{4}- \dfrac{1}{5} [/tex]
După reduceri, suma algebrică din enunț devine:
[tex] \it \dfrac{^{5)}1}{\ 2} - \dfrac{^{2)}1}{\ 5}- \dfrac{3}{10} = \dfrac{5-2-3}{10} = \dfrac{0}{10} = 0 [/tex]