שינויים

<math>a_{2n}-a_n =a_{2n}-a_{2n-1}+a_{2n-1}-...+a_{n+1}-a_n= \frac{1}{2n} + \frac{1}{2n-1}+ ... + \frac{1}{n+1} \leq geq \frac{1}{2n} + \frac{1}{2n}+ ... + \frac{1}{2n} = n\cdot \frac{1}{2n} = \frac{1}{2}</math>