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suma gaus 1+2+3...+1000= ; 1+2+3+...2001= ; 1+2+3+...50. va rog ajutati-ma urgent

Răspuns :

[tex]\displaystyle a).1+2+3+...+1000= \frac{1000(1000+1)}{2} = \frac{1000 \cdot 1001}{2} = \\ \\ = \frac{1001000}{2} =500500 \\ \\ b).1+2+3+...+2001= \frac{2001(2001+1)}{2} = \frac{2001 \cdot 2002}{2} = \\ \\ = \frac{4006002}{2} =2003001 \\ \\ c).1+2+3+...+50= \frac{50(50+1)}{2} = \frac{50 \cdot 51}{2} = \frac{2550}{2} =1275 [/tex]

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