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calculati :
8+16+24+32+...+4000=

am mare nevoie!!!


Răspuns :

[tex]\displaystyle 8+16+24+32+...+4000=8(1+2+3+...+500)= \\ \\ =8 \times \frac{500(500+1)}{2} =8 \times \frac{500 \times 501}{2} =8 \times \frac{250500}{2} = \\ \\ =8 \times 125250=1002000[/tex]