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Efectuati
a) 1+2+3+...+49+50=
b) 20+21+22+...+49+50=

Răspuns :

Bogdantorres
1+2+3+...+49+50=
(1+49)+(2+48)+(3+47)+...+(24+26)+25+50=
50+50+50+...+50(de 24 de ori)+75=
50x24+75=
1200+75=1275


1+2+3+...+49+50                                                                                                       50+49+48+...+1              51+51+51...+51        (51-1)/1+1=50/1+1=51       51/1=51   


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