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Calculati urmatoarele sume:

S=2+4+6+.......+1000



Răspuns :

2x(1+2+3+4+5+...+500)=S
2x(250x501)=S
2x125250=S
S=250500
2+4+6+.......+1000=2(1+2+3+......+500)  In paranteza avem suma lui Gauss
S=2[(500
×501) / 2]=500×501=250 500