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a fost răspuns

Calculati sumele: a) S =1+2+3+... .+400;
B)T= 43+44+45+... ... + 400;

C) U= 7+14+21+... ....+2800

Răspuns :

Christian02
a)  = 400*401/2=200*401=80200
b)  = (400-43+1)(400+43) : 2 = 358 * 443 : 2 = 179* 443 = 79297
c)  = (2800-7 : 7  +  1) (7+2800) :2 = (2793 :7   +1)* 2807 = (399+1)*2807 =
= 1122800
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Succes!

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