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Cum se rezolva:
2+3+4+...+50=


Răspuns :

nr termenilor= (50-2):1+1=48+1=49
Suma= [(50+2)*49]:2=52*49:2=2548:2=1274
[tex]\displaystyle 2+3+4+...+50= \frac{50(50+1)}{2}-1= \frac{50 \times 51}{2} -1= \frac{2550}{2} -1= \\ \\ = 1275-1=1274[/tex]