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Calculati 2+4+6+8+...+4000

Pls am need urgent!!!

Dau 15 puncte!!!


Răspuns :

Aplicam suma lui Gauss:
S=2+4+6+8+...+4000
S=2×1+2×2+2×3+2×4+...+2×2000
S=2 (1+2+3+...+2000)
S=2×2000×2001:2
S=2000×2001
S=4002000
Se foloseste Suma lui Gauss.
2+4+6+8+.....+4000=2(1+2+3+4+....+2000)=2[2000×(2000+1)]:2=
2000×2001=4 002 000