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1+2+3+4-5+6+7+8+9-10+...+91+92+93+94-95 pls va roggg rezolvati

Răspuns :

1+2+3+4-5+6+7+8+9-10+...+91+92+93+94-95 =
adunam si scadem 5+10+15...+95 = 5(1+2+3+....19)=5*19*20/2=950
si vom obtine 1+2+3+....95-950*2=95*96/2-1900=4560-1900=2660