Question

Calcular soma dos termos da P.A (-16-,14-13,..,84).

Answer 1

An = 84
A1= - 16
A2 = - 14
R = a2-a1
R= -14-(-16)
R= -14+16
R = 2

An = a1 + (n -1).r
84= - 16 +(n -1).2
84+16= 2n-2
100= 2n-2
100+2= 2n
102= 2n
2n =102
N = 102/2
N= 51

SN = (a1+an).n/2

S51 = (a1+a51).51/2
S51= (-16+84).51/2
S51= 68.51/2
S51 = 34.51
S51= 1734