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Calculati:
2+4+6+....+100-(1+3+5+...+99)=
Dau Coroana!!


Răspuns :

2+4+6+....+100-(1+3+5+...+99)=
=(1+1+3+1+5+1+...+99+1)-
(1+3+5+...+99)=
=(1+3+5+...+99+50)-(1+3+5+...+99)=50
2(1+2+3+4+5+6+7+....+50)=
=2[50(50+1): 2]
=2(25*51)
=2*1275
=2550
1+3+5+...+99=
=100*50/2=50*50=2500
2550-2500=50