Facem in felul urmator: aflam intai f(1),inlocuim f(x) cu f(1),in loc de x punem 1.
[tex]f(x)=x^2-4x+5=\ \textgreater \ \\
f(1)=1^2-4*1+5\\
f(1)=2[/tex]
Aflam in acelas mod f(2);f(3) si f(9).
[tex]f(2)=2^2-4*2+5=\ \textgreater \ f(2)=1\\
f(3)=3^2-4*3+5=\ \textgreater \ f(3)=2\\
--------------------------\\
f(9)=9^2-4*9+5=\ \textgreater \ f(9)=50[/tex].
Scriem sub forma de suma Gauss
[tex]2+1+2+3+...+50=[/tex]
Aplicam formula [n(n+1)]:2
[tex]2+ \frac{[50(50+1)]}{2} =\ \textgreater \ 2+1275=\ \textgreater \ S_n=1277[/tex]