Salut!
16.
f(1) = 1
f(2)= 3
f(3) = 5
cum f(2) = (f(1) +f(3))/2 = f1 +f2+f3...+f6 = o progresie aritmetica
=>a1=1
r=2
f(6) = 11 => S6=(a1+f6)x6/2 = 12 x 6 / 2 =36
17.f(-6) = -9
f(0)= -3
f(6) = 3
f(12) = 9
S= -9 + 3 - 3 - 9 = 0
18.Se rezolva ca 16, doar ca adaugi si f(0) pentru a demonstra progresia.
