Question

metoda lui gaus rezolvare completa 3+5+7+....1001-2-4-6-...-1000

Answer 1

3+5+7+....1001-2-4-6-...-1000=
=3-2+5-4+.....+1001-1000=
=1+1+...1(de 499 ori deoarece incepe de 3-2..nu de la 2-1)=
=499

Answer 2

 3+5+7+....1001     
- 2-4-6-...-1000
---------------------
1+1+1+.......1

2n-1=3      2n-1= 1001
2n=4          2n= 1002
n=2            n=  501          Avem 500 -1 = 499 termeni


3+5+7+....1001-2-4-6-...-1000  = 499

Varianta a IIa


3+5+7+....1001-(2+4+6+...+1000) = (3+1001)*500/2 -1  - 2* (1+2+3...+500)=

= 250999- 2*500*501/2=250999-250500=499