Question

b=1+3+5+7+...+2015 va

Answer 1

b=1+3+5+7+...+2015

b=(1+2+3+4+...+2015)-(2+4+6+...+2014)

b=2015x2016/2 - 2(1+2+3+...+1007)

b=2015x1008 - 2x 1007x1008/2

b=2015x1008 - 1007x1008

b=1008(2015-1007)

b=1008x1008

b=1008²

sau

b=1.016.064

Succes!

Answer 2

Răspuns:

Explicație pas cu pas:

Formula generala pentru suma de numere impare consecutive este:

1 + 3 + 5 + ... + 2n-1 = n^2

2n-1=2015  = >  2n=2016  = > n = 2016/2 = 1008

b=1+3+5+7+...+2015  =  1008² =  1016064