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Oannaionela97
a fost răspuns

Scrie sub forma zecimala fractia : [tex] \frac{7 +14 +21+..........+210}{30} [/tex].

Răspuns :

[tex]7+14+21+...+210=7*(1+2+3+4+...+30)= \frac{7*(30*31)}{2} [/tex]
[tex]7*15*31=3255[/tex]
[tex] \frac{3255}{30} = \frac{651}{6} = \frac{217}{3} [/tex]
Flavistin
[tex]\frac{7+14+21+....+210}{30}= \\ \frac{7*(1+2+3+........+30)}{30}= \\ \frac{7*30*(30+1)/2}{30}= \\ \frac{210*31/2}{30}= \\ \frac{6510/2}{30}= \\ \frac{3255}{30}= \\ 108,5[/tex]

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