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1+7+3+19+...+601
Va rog repede!!!​


Răspuns :

Răspuns:

1+7+13+19+...+601;    forma sirului ;    6x-5 ;    6x-5=601 ;    6x=606 ;    x=606/6=101 ;  sirul are 101 termeni ;    s=(1+101)*101/2=52*101=5252

Explicație pas cu pas:

 

Consider ca suma este: (vezi comentariile)

1+7+13+19+...+601

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[tex]\displaystyle\bf\\1 + 7 + 13 + 19 + ... + 601=?\\\\Calculam~numarul~de~termeni:\\\\n=\frac{601-1}{6}+1=\frac{600}{6}+1=100+1=101~de~termeni.\\\\1 + 7 + 13 + 19 + ... + 601=\\\\=\frac{n(601+1)}{2}=\frac{101\times602}{2}=101\times301=\boxed{\bf30401}[/tex]