Răspuns:
3/7
Explicație pas cu pas:
[tex]a = \frac{5 - 3}{3 \times 5} + \frac{8 - 5}{5 \times 8} + \frac{13 - 8}{8 \times 13} + \frac{21 - 13}{13 \times 21} = \frac{1}{3} - \frac{1}{5} + \frac{1}{5} - \frac{1}{8} + \frac{1}{8} - \frac{1}{13} + \frac{1}{13} - \frac{1}{21} = \frac{1}{3} - \frac{1}{21} = \frac{6}{21} = \frac{3}{7}[/tex]
