Question

F(x) = 2x - 1
Calculati F(1) + F(2) + ... F(21).

Answer 1

Răspuns:

F(1)= 2×1-1

F(2)=2×2-1

......

F(21)= 2×21-1

S= 2(1+2+3+....+21)-21

S=2[21(21+1) / 2] - 21= 2(21×22/2)-21= 2(21×11)-21= 2×231-21= 462-21=441

Explicație pas cu pas:

Am folosit Suma lui Gauss