a) S₁ = 1+2+3+...+20
S₁ = (20*21):2
S₁ = 10*21
S₁ = 210
S₂ = 1+2+3+...+24
S₂ = (24*25):2
S₂ = 12*25
S₂ = 280
[S₁;S₂] = 2³ x 3 x 5 x 7 = 840
b) S₁ = 1+2+3+...+27
S₁ = (27*28):2
S₁ = 27*14
S₁ = 378
S₂ = 1+2+3+...+35
S₂ = (35*36):2
S₂ = 35*18
S₂ = 630
[S₁;S₂] = 3³ x 2 x 5 x 7 = 1890
c) S₁ = 1+2+3+...+26
S₁ = (26*27):2
S₁ = 13*27
S₁ = 351
S₂ = 1+2+3+...+39
S₂ = (39*40):2
S₂ = 39*20
S₂ = 780
[S₁;S₂] = 2² x 3³ x 5 x 13 = 7020
Sper ca te-am ajutat.