f(1)= 1+2 = 3
f(2) = 2+2 =4
f(3) = 3+2 = 5
....
f(49)=49+2=51
f(50)=50+2=52
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Tragi linie si aduni
f(1)+f(2)+f(3)+...+f(50)= 1+2+3+4+5+6+7....+50+2*50
Pentru suma de la 1 la 5 se aplica formula 1+2+3...+n=n*(n+1)/2 adica
50*(50+1)= 50*49=2450
Revenind la suma S= 2450+100=2550