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Barosanubogdan
a fost răspuns

Rezolva:
a) 5+10+15+20+... +500=
b) 1+3+5+7+... +99=?

Răspuns :

Denispanait
a) 5(1+2+3+4+...+100)=5 (100*+101/2)=5 (50*101)=250*5005, de aici alfa tu
b)(1+2+3+4+...+100) - (2+4+6+...+100)
=(100*101/2)-2*(1+2+3+...+50)
=50*101-2*(50*51/2)
=50*101-2 (25*51)
=50*101-50*102
=-50

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