Răspuns :

Ska3ferid

Răspuns:

3+5+9+__5__+1999+2001-2-4-6-8- 10-1998-2000=1

Explicație pas cu pas:

Hi-hi

Andrutaandruid
3+5+7+9+...+1999+2001-2-4-6-8-...-1998-2000=
= 3+5+7+9+...+1999+2001-2(1+2+3+4+...+1000)=
= 3+5+7+9+...+1999+2001-2* =
= 3+5+7+9+...+1999+2001-1000*1001=
=1+2+3+4+...+2000+2001-2-4-6-8-...-2000-1-1000*1001=
= -2(1+2+...+1000)-1000*1001-1=
=1001*2001-1001*1000-1000*1001-1=
=1001(2001-1000-1000)-1=
=1001-1=1000

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