👤

HELP MY PLS!! RELOLVA:15+16+17...+70
REPEDE VA ROG


Răspuns :

s=(15+70)x56 ( totul supra 2)
s= 85x28 (56 se reduce cu 2)
s=2380
=(1+2+3+....+15+16+...+70)-(1+2+3+...+14)=(71*70:2)-(14*15:2)=(71*35)-(7*15)=2485-225=2260