[tex]S=\frac{1}{2}+\frac{1}{6}+...+\frac{1}{9900}\\
\\
S=\frac{1}{1\cdot 2}+\frac{1}{2\cdot 3}+....+\frac{1}{99\cdot 100}\\
\\
S=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+....+\frac{1}{99}-\frac{1}{100}\\
\\
S=1-\frac{1}{100}\\
S=\frac{99}{100}\\
Cum\ 99\ \textless \ 100\Rightarrow Fractia\ este\ subunitara.[/tex]