Question

Calcule a soma dom 100 primeiros termos da PA (1, 1/2, ......).

Answer 1

an = a1 + (n-1)r
an = 1 + (100-1) -1/2
an = 1 + 99. -1/2
an = 1 -99/2
an = -97/2

Sn = (a1 + an)n
               2
Sn = (1 -97/2) 100
                 2
Sn= -95/2 . 50
Sn = - 4750/2
Sn = - 2 375