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Calculeaza!!!
2+4+6+........+1000=
3+6+9+........+2013=
5+10+15+....+500=
7+14+21+....+700=


Răspuns :

S =        2+    4+   6.....+996+998+1000
S  =  1000+998+996.....+   6+    4+     2
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2 S = 1002+1002+1002+.........+1002+1002+1002
Stabilim cati termeni are suma
2, 2+2*1, 2+3*1.............2+2*499
suma  are  500  de  termeni
2S = 1002*500
2S = 501000
s = 501000: 2
S = 250500
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