Question

calculati 3⁺6⁺9⁺12⁺......⁺ 2019 4plus8plus12plus......2020 5plus10plus15plus20plus ....plus 2020 7plus14plus21plus......plus2023

Answer 1

1) 3(1+2+3+4+....+673)=3x673x674/2=680.403
2) 4(1+2+3+4+....+505)=4x505x506/2=511.060
3) 5(1+2+3+4+....+404)= 5x404x405/2=409.050
4) 7(1+2+3+4+.....+289)=7x289x290/2=293.335 cu formula lui Gauss:

suma unei progresii aritmetice cu n termeni este

S=n(a1+an)/2, unde a1 si an sunt primul si ultimul termen ai progresiei

succes!