Cevap:
[tex]\frac{1}{18}[/tex]
Adım adım açıklama:
[tex]\frac{1}{9.10} =\frac{1}{9} -\frac{1}{10} \\\\\frac{1}{10.11} =\frac{1}{10} -\frac{1}{11} \\...[/tex]
[tex]\frac{1}{9.10} +\frac{1}{10.11} +\frac{1}{11.12} +...+\frac{1}{17.18} =\\\\\frac{1}{9} -\frac{1}{10} +\frac{1}{10} -\frac{1}{11} +\frac{1}{11} -...+\frac{1}{17} -\frac{1}{18} =\\\\\frac{1}{9} -\frac{1}{18} =\frac{2}{18} -\frac{1}{18} =\frac{1}{18}[/tex]
