Question

1+2+...+999=
Vreau rezolvarea prin asocierea nr

Answer 1

1+999=1000
2+998=1000
3+997=1000
...
499+501=1000
prin adunare rezulta ca suma este 499x1000+500=499500

Answer 2

folosesti formula: Sn=n(n+1)/2 = 999(999+1)/2=(999*1000)/2=999*500=499500