Question

Calculati:
a) 1+2+3+...+2017;
b) 2+4+6+...+2018;
c) 1+3+5+...+2017.

Answer 1

ti l fac si pe ultimul acum

Answer 2

a) 1+2+3+....+2017 = (1+2017) * 2017 / 2 = 2017*1009 = 2035153
b) 2+4+6+....+2018 = (2+2018) * 1009 / 2 = 1009 * 1010 = 1019090
c) 1+3+5+....+2017 = (1+2017) * 1009 / 2 = 1009 * 1009 = 1018081
* = inmultire
S = (a₁+aₓ) * x / 2   ; 
a₁ = primul termen ; aₓ = ultimul termen ; x = nr. de termeni