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4+8+12+...+2000 metoda gauss

Răspuns :

[tex]\displaystyle 4+8+12+...+2000=4(1+2+3+...+500)=4 \times \frac{500(500+1)}{2} = \\ \\ =4 \times \frac{500 \times 501}{2} =4 \times \frac{250500}{2} =4 \times 125250=501000[/tex]
4+ 8+ 12+ ...+2 000=
1+2+3+ ... +4·500=
4·(1+ 2+ 3+ ...+ 500)=
500·501:2=
2·500·501=
1 000·501=
501 000