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Calculati numerele : s1= 1+2+3...+50 , s2= 1+2+3+...+35 , s3= 1+3+5+...+99 , s4= 2+4+6+...+100

Răspuns :

s1 este egal cu 1275
S1=1+2+3....+50=
50*(50+1):2=
50*51:2=1275
S2=1+2+3+.....+35=
35*(35+1):2=
35*36:2=630
S3=1+3+5+....+99=
100:2=50
50*(99+1):2=
50*100:2=2500
S4=2+4+6+.....+100=
100:2=50
50*(100+2):2=
50*102:2=2550