Răspuns :

Miky93id
10(1+2+3+.......+123)= 10* (1+123)*123/2=

=5*124*123=76 260

7(1+2+3+....+45)=7* (1+45)*45/2=   7*46*45/2=  7*23*45=  7 245
Pgabrielacasandid
10*(1+2+3+...+123)=7*(1+2+3+...+45)
S123=(123*124):2=7626
S45=(45*46):2=1035
10*7626=7*1035
76260=7245

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